CHAPTER 3 ATOMS ATOMS MATTER 10/17/2016. Matter- Anything that takes up space (volume) and has mass. Atom- basic unit of matter.

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1 CHAPTER 3 MATTER Matter- Anything that takes up space (volume) and has mass. Matter Combining Matter States of Matter Atom- basic unit of matter. Subatomic particles- protons, neutrons, and electrons. ATOM MODELS ATOMS Protons are positively charged subatomic particles (+) Neutrons are neutrally charged subatomic particles (no charge) Protons and Neutrons are found in the nucleus (center) of an atom. Protons and neutrons make up the mass of an atom (atomic mass). ATOMS Electrons are negatively charged particles that orbit around the nucleus. Electrons are attracted to the nucleus and are in constant motion. Atoms have no charge because they have equal number of protons as electrons. (Positive) + (Negative) = No net charge ELEMENTS Element- a pure substance that consists entirely of one type of atom. There are more than 100 known elements Elements are represented as either one or two letters and are listed on the periodic table. Elements are listed on the periodic table by the number of protons/electrons that they have. 1

2 SYMBOLS FOR ELEMENTS All elements are classified and arranged according to their chemical properties in the periodic table of elements. The number of protons and neutrons in atoms of different elements varies widely. Atomic number is the number of protons in an atoms nucleus. Atomic mass = # Protons + # Neutrons VALENCE ELECTRONS The electrons in the outermost energy level determine the chemical behavior of the different elements. The outermost electrons are called valence electrons HOW MANY VALENCE ELECTRONS DOES CARBON HAVE? IDENTIFYING ATOMS 2

3 IDENTIFYING ATOMS IDENTIFYING ATOMS IDENTIFYING ATOMS ELECTRONS Electrons occupy areas around the nucleus of an atom called energy levels The innermost energy level can only hold 2 electrons. The second energy level is larger, it can hold up to 8 electrons. ISOTOPES Isotopes- atoms of an element that have different number of neutrons. Isotopes have a different atomic mass, but the same atomic number. Because they have the same number of electrons, all isotopes of an element have the same chemical properties. Radioactive isotopes- have unstable nuclei that break down at a constant rate over time, and are used for dating purposes, and tracers. 3

4 ISOTOPES OF CARBON IONS An atom that loses electrons becomes positively charged (+) An atom that gains electrons becomes negatively charged (-) Positively and negatively charged atoms are called IONS Ions are atoms that either gain or lose electrons VOCABULARY: VOCABULARY: Matter: anything that takes up space (volume) and has mass. Neutron: particles found in the nucleus of an atom that have no charge. Element: a pure substance that consists entirely of one type of atom. Electron: negatively charged particles that orbit around the nucleus. Nucleus: the center of the atom which contains the protons and neutrons Atomic Number: the number of protons in an atoms nucleus. Proton: positively charged particles that make up the nucleus of an atom Atomic Mass: # Protons + # Neutrons VOCABULARY: Isotopes: Ions: Atoms of the same element that have a different number of neutrons (different atomic mass). An atom which gains or loses an electron and has a net electric charge CHEMICAL COMPOUNDS Most elements in nature are found combined with other elements. Compound- a substance formed by the chemical combination of two or more elements in specific proportions. Chemical formula- the composition of compounds in terms of types of elements, and numbers of each. 4

5 CHEMICAL BONDS CONTINUED Molecule- the smallest unit of most compounds (ex. H 2 0) Molecules have no overall electric charge. Molecules form covalent bonds CHEMICAL COMPOUNDS Examples of compounds and chemical formulas. H 2 O CO 2 C 6 H 12 O 6 NaCl HCl CHEMICAL COMPOUNDS NaCl = Sodium Chloride = Table Salt Combination of sodium and chlorine CHEMICAL BONDS Atoms in compounds are held together by chemical bonds. Ions atoms that lose or gain electrons Ionic bond- is formed when one or more electrons are transferred from one atom to another (ex. NaCl). IONIC BOND CHEMICAL BONDS CONTINUED Covalent bond- situation where elements share electrons between them, instead of transferring them. Electrons travel in the energy levels of both atoms in a covalent bond. 5

6 CHEMICAL BONDS CONTINUED Metallic bond- valence electrons are shared between all atoms. Electrons flow through metals This flow allows metals to conduct electricity. METALLIC BOND Valence electrons move freely around positively charged ions of the metal. CHEMICAL REACTIONS: The change of one or more substance into another substance is called a chemical reaction. Bonds holding atoms together are rearranged during a chemical reaction: PHOTOSYNTHESIS CO 2 + H 2 O C 6 H 12 O 6 + O 2 Ex: H 2 + O 2 H 2 O Fe + O 2 Fe 2 O 3 Reactant + Reactant Product 6

7 DRAWING MOLECULES SOLUTIONS AND SUSPENSIONS Mixtures- a combination of two or more components that retain their identities. Ex: cinnamon and sugar, salt water Solution- a mixture in which one or more substances are uniformly distributed in another substance. Ex: Seawater, air, kool-aid ACIDS AND BASES Acid: a solution containing a substance that produces hydrogen ions (H + ) in water. Base: a substance that produces hydroxide ions (0H - ) in water. Neutral: a solution which has equal proportions of H + and 0H - ions in water. ACID BASE 7

8 ph SCALE The ph scale is a measure of how acidic or basic a substance is. It directly measures the concentration of H + ions in solution. CHEMICAL COMPOUNDS Most elements in nature are found combined with other elements. Compound- a substance formed by the chemical combination of two or more elements in definite proportions. Chemical formula- the composition of compounds in terms of types of elements, and numbers of each. PROPERTIES OF WATER Water covers over 75% of the Earth s surface. Water is the single most abundant compound in most living things. It is a liquid at most of Earth s temperatures. It expands when it freezes and is less dense than liquid water. It is neutral in charge, but polar. Polarity- an uneven distribution of electrons. PROPERTIES OF WATER Water is the universal solvent because it dissolves more substances than any other liquid. Pure water is 7.0 on the ph scale (Neutral). Water moves against the force of gravity due to capillary action. Water has a high surface tension and a high specific heat index. CHEMICAL COMPOUNDS Most elements in nature are found combined with other elements. Compound- a substance formed by the chemical combination of two or more elements in definite proportions. Chemical formula- the composition of compounds in terms of types of elements, and numbers of each. 8

9 CHEMICAL COMPOUNDS Examples of compounds and chemical formulas CHEMICAL COMPOUNDS NaCl = Sodium Chloride = Table Salt Combination of sodium and chlorine H 2 O CO 2 C 6 H 12 O 6 NaCl HCl SOLUTIONS AND SUSPENSIONS Mixtures- a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. Solution- a mixture in which one or more substances are uniformly distributed in another substance. Solutions can be a liquid, solid, or gas, or any combination. BELL RINGER Draw the Bohr model of the following atoms: Hydrogen Carbon Nitrogen Oxygen HYDROGEN CARBON 9

10 NITROGEN OXYGEN VALENCE ELECTRONS The electrons in the outermost energy level determine the chemical behavior of the different elements. The outermost electrons are called valence electrons HOW MANY VALENCE ELECTRONS? Hydrogen? Carbon? Nitrogen? Oxygen? ISOTOPES Isotopes- atoms of an element that have different number of neutrons. ISOTOPES OF CARBON 10

11 CHEMICAL COMPOUNDS Most elements in nature are found combined with other elements. Compound- a substance formed by the chemical combination of two or more elements in definite proportions. Chemical formula- the composition of compounds in terms of types of elements, and numbers of each. CHEMICAL COMPOUNDS Examples of compounds and chemical formulas H 2 O CO 2 C 6 H 12 O 6 NaCl HCl CHEMICAL COMPOUNDS NaCl = Sodium Chloride = Table Salt VOCABULARY: Matter: anything that takes up space (volume) and has mass. Combination of sodium and chlorine Element: Nucleus: Proton: a pure substance that consists entirely of one type of atom. the center of the atom which contains the protons and neutrons positively charged particles that make up the nucleus of an atom VOCABULARY: VOCABULARY: Neutron: Electron: Atomic Number: particles found in the nucleus of an atom that have no charge. negatively charged particles that orbit around the nucleus. the number of protons in an atoms nucleus. Isotopes: Ions: Atoms of the same element that have a different number of neutrons (different atomic mass). An atom which gains or loses an electron and has a net electric charge Atomic Mass: # Protons + # Neutrons 11

12 CHEMICAL FORMULAS Carbon is written first if it is present in the molecule. Oxygen is written at the end of the formula. Hydrogen is written directly after carbon if both are present. CHEMICAL BONDING Hydrogen can make 1 bond (1 V.E.) Carbon can make 4 bonds (4 V.E.) Nitrogen can make 3 bonds (5 V.E.) Oxygen can make 2 bonds (6 V.E.) BUILDING MODELS H 2 O BUILDING MODELS CO 2 12

13 BUILDING MODELS NH 3 BUILDING MODELS C 2 H 2 BUILDING MODELS CH 4 13

14 BUILDING MODELS C 3 H 8 CHEMICAL REACTIONS Atoms can combine to form compounds, or break down into simpler substances. Matter cannot be created or destroyed The number of atoms that enter a chemical reaction are equal to the number of atoms after the chemical reaction. CHEMICAL REACTIONS Chemical reaction- a process that changes one set of chemicals into another set of chemicals. Reactants- elements or compounds that enter a reaction. Products- elements or compounds that are produced by a chemical reaction. CHEMICAL REACTIONS Chemical reactions must be balanced since matter cannot be created or destroyed. This is called The law of conservation of matter. WHAT IS A CHEMICAL EQUATION? A chemical equation is a short-hand way of writing a chemical reaction. Reactants are on the left of the equation. Products are on the right. Mg + 2HCl MgCl 2 + H 2 reactants products 14

15 CHEMICAL REACTIONS BELL-RINGER Atoms are not CREATED or DESTROYED during a chemical reaction. Scientists know that there must be the SAME number of atoms on each SIDE of the EQUATION. To balance the chemical equation, you must add COEFFICIENTS in front of the chemical formulas in the equation. You cannot ADD or CHANGE subscripts! Balance the following equations. H 2 + O 2 H 2 O CO+ O 2 CO 2 REVIEW QUESTIONS (3.1) 1. Differentiate among the three parts of an atom in terms of their location, charge, and mass. 2. Explain why the elements magnesium and calcium have similar properties. 3. How does a neutral atom become an ion? REVIEW QUESTIONS (3.1) 4. Compare and contrast these isotopes: uranium-239 uranium-238 uranium Draw a model of a calcium atom, including the number and position of protons, neutrons, and electrons in the atom. 6. Why is the atomic mass of most elements not a whole number? REVIEW QUESTIONS (3.1) 7. As the radioactive isotope radium-266 decays, it emits two protons and two neutrons. How many protons and neutrons are now left in the nucleus? What is the atom s new atomic number? What is the name of this element? 86 protons 136 neutrons Atomic number = 86 = radon. REVIEW QUESTIONS (3.2) 1. Explain why molecules do not have electric charges. 2. Differentiate between molecules and compounds. 3. (Skip) (all compounds are molecules, but not all molecules are compounds) 4. How can an acid be neutralized? 5. Compare and contrast mixtures and solutions 15

16 BELL RINGER: What is the chemical formula for water? What does the chemical formula represent? What is the difference between frozen water and liquid water? SECTION 3.3: STATES OF MATTER All matter on Earth and in the universe occurs in the form of a solid, a liquid, a gas, or plasma. 16

17 SOLIDS CRYSTALLINE STRUCTURE OF DIAMOND Solids are substances with densely packed particles, which can be ions, atoms, or molecules. Most solids are crystalline structures because the particles of a solid are arranged in regular geometric patterns. SOLIDS Some solid materials have no regular internal patterns. Glass is a solid that consists of densely packed atoms arranged randomly. Glass does not form crystals. 17

18 LIQUIDS At any temperature above absolute zero (-273 C), the atoms in a solid vibrate. Vibrations increase with increasing temperature (thermal vibrations) At melting point, vibrations become vigorous enough to break the forces holding the solid together. LIQUIDS Liquids take the shape of their container Liquids also have a definite volume. GASES The particles in liquid move and vibrate vigorously. Some particles gain enough energy to escape the liquid. The process from changing from a liquid to a gas is called evaporation. When any liquid reaches its boiling point, it vaporizes quickly as a gas. PLASMA When a gas is heated to a temperature of 5000 C, particles are so violent that electrons are knocked away from atoms and give off light. The gases of stars, lightning, and neon signs are all examples of matter in a plasma state. 18

19 CHANGES OF STATE When some solids are heated, they become liquid in a process called melting When a liquid is heated to the boiling point, it absorbs enough thermal energy to evaporate and become a gas. CHANGES OF STATE When a gas is cooled, it becomes a liquid in a process called condensation A change of state from a solid into a gas is called sublimation. The positively charged particle in an atom is called the: A. neutron B. ion C. proton D. electron The positively charged particle in an atom is called the: A. neutron B. ion C. proton D. electron 19

20 The electrically neutral particle in an atom are called A. neutrons B. ions C. protons D. electrons The electrically neutral particle in an atom are called A. neutrons B. ions C. protons D. electrons The atomic mass of an atom is equal to the sum of the A. protons and electrons B. neutrons and electrons C. protons and neutrons D. protons only The atomic mass of an atom is equal to the sum of the A. protons and electrons B. neutrons and electrons C. protons and neutrons D. protons only Atoms of an element that differ by their mass number are called A. ions B. isotopes C. compounds D. bosons Atoms of an element that differ by their mass number are called A. ions B. isotopes C. compounds D. bosons 20

21 What is the atomic number of this atom? A. 3 B. 4 C. 5 D. 6 What is the atomic number of this atom? A. 3 B. 4 C. 5 D. 6 How many valence electrons does this atom have? A. 1 B. 2 C. 3 D. 4 How many valence electrons does this atom have? A. 1 B. 2 C. 3 D. 4 Which element does this atom represent? A. He B. Be C. Li D. N Which element does this atom represent? A. He B. Be C. Li D. N 21

22 The figure shows the arrangement of atoms in a substance. What is this substance? A. gas B. glass C. liquid D. solid The figure shows the arrangement of atoms in a substance. What is this substance? A. gas B. glass C. liquid D. solid What kind of ion is characteristic of an acid? A. oxygen ion B. negative ion C. hydroxide ion D. hydrogen ion What kind of ion is characteristic of an acid? A. oxygen ion B. negative ion C. hydroxide ion D. hydrogen ion During the process of sublimation, ice is converted into. A. hydrogen and hydroxide ions B. hydrogen C. liquid water D. water vapor During the process of sublimation, ice is converted into. A. hydrogen and hydroxide ions B. hydrogen C. liquid water D. water vapor 22