Unit 3: The Atom Part 1. DUE: Friday October 13, 2017

Transcription

1 Unit 3: The Atom Part 1 The following pages are practice questions for this unit, and will be submitted for homework! You must complete: What is in an atom? ALL QUESTIONS Calculating the Number of Protons, Neutrons, and Electrons ALL QUESTIONS Calculating Average Atomic Mass o Questions 1-3 ALL QUESTIONS o Questions OPTIONAL History of Atomic Structure ALL QUESTIONS Practice Regents Questions ALL QUESTIONS DUE: Friday October 13,

2 What is in an Atom? Directions: Use your knowledge of chemistry to fill in the table below. Subatomic Particle Location Charge Relative Mass Neutron Proton Electron Directions: Label the parts of an atom. Write your answer on the arrow Calculating the Number of Protons, Neutrons, and Electrons Directions: Using your reference table and your knowledge of chemistry, fill in the following chart. Element Symbol Name Silver Atomic Number Atomic Mass Mass Number # of Protons # of Electrons # of Neutrons C Zn 5 25 Kr

3 Calculating Average Atomic Mass Directions: Using your reference table and your knowledge of chemistry, calculate the average atomic mass. 1. Chlorine has 2 naturally occurring isotopes. Using the information provided below, calculate the average atomic mass for chlorine. SHOW ALL WORK Isotope Natural Abundance on Earth (%) Atomic Mass (amu) 35 Cl Cl Titanium has 5 naturally occurring isotopes. Using the information provided below, calculate the average atomic mass for titanium. SHOW ALL WORK. Isotope Natural Abundance on Earth (%) Atomic Mass (amu) Ti Ti Ti Ti Ti Natural samples of copper contain two isotopes. 63 Cu has a mass of amu and 65 Cu has a mass of amu. The percent abundance of 63 Cu is 69.09%. Calculate the average atomic mass of copper. 3

4 4. OPTIONAL: Calculate the atomic mass of an element if 60.4% of the atoms have a mass of amu and the rest have a mass of amu. Identify the element in the periodic table. 5. OPTIONAL: Europium has two stable isotopes: 151 Eu with a mass of amu and 153 Eu with a mass of If elemental Europium is found to have a mass of amu on earth, calculate the percent of each of the two isotopes. 4

5 History of Atomic Structure John Dalton ( ): John Dalton was an English chemist. His ideas form the atomic theory of matter. Here are his ideas. All elements are composed (made up) of atoms. It is impossible to divide or destroy an atom. All atoms of the same elements are alike. (One atom of oxygen is like another atom of oxygen.) Atoms of different elements are different. (An atom of oxygen is different from an atom of hydrogen.) Atoms of different elements combine to form a compound. These atoms have to be in definite whole number ratios. For example, water is a compound made up of 2 atoms of hydrogen and 1 atom of oxygen (a ratio of 2:1). Three atoms of hydrogen and 2 atoms of oxygen cannot combine to make water. 1. What is the name of John Dalton s theory? 2. What are elements made of? 3. An atom of hydrogen and an atom of carbon are 4. What are compounds made of? 5. The ratio of atoms in HCl is: a) 1:3 b) 2:1 c) 1:1 J. J. Thompson (Late 1800s): J. J. Thompson was an English scientist. He discovered the electron when he was experimenting with gas discharge tubes. He noticed a movement in a tube. He called the movement cathode rays. The rays moved from the negative end of the tube to the positive end. He realized that the rays were made of negatively charged particles electrons. 1. What did J.J. Thompson discover? 2. What is the charge of an electron? 3. What are cathode rays made of? 4. Why do electrons move from the negative end of the tube to the positive end? 5. What was Thompson working with when he discovered the cathode rays? 5

6 Lord Ernest Rutherford ( ): Ernest Rutherford conducted a famous experiment called the gold foil experiment. He used a thin sheet of gold foil. He also used special equipment to shoot alpha particles (positively charged particles) at the gold foil. Most particles passed straight through the foil like the foil was not there. Some particles went straight back or were deflected (went in another direction) as if they had hit something. The experiment shows: Atoms are made of a small positive nucleus; positive nucleus repels (pushes away) positive alpha particles Atoms are mostly empty space 1. What is the charge of an alpha particle? 2. Why is Rutherford s experiment called the gold foil experiment? 3. How did he know that an atom was mostly empty space? 4. What happened to the alpha particles as they hit the gold foil? 5. How did he know that the nucleus was positively charged? Niels Bohr (Early 1900s): Niels Bohr was a Danish physicist. He proposed a model of the atom that is similar to the model of the solar system. The electrons go around the nucleus like planets orbit around the sun. All electrons have their energy levels a certain distance from the nucleus. Each energy level can hold a certain number of electrons. Level 1 can hold 2 electrons, Level 2-8 electrons, Level 3-18 electrons, and level 4 32 electrons. The energy of electrons goes up from level 1 to other levels. When electrons release (lose) energy they go down a level. When electrons absorb (gain) energy, they go to a higher level. 1. Why could Bohr s model be called a planetary model of the atom? 2. How do electrons in the same atom differ? 3. How many electrons can the fourth energy level hold? 4. Would an electron have to absorb or release energy to jump from the second energy level to the third energy level? 5. For an electron to fall from the third energy level to the second energy level, it must energy. 6

7 Practice Regents Questions 1. The table below gives the masses of two different subatomic particles found in an atom. Subatomic Particle and Their Masses Subatomic Particle Mass (g) X 1.67 x Z 9.11 x Which of the subatomic particles are each paired with their corresponding name? a. X, proton and Z, electron c. X, neutron and Z, proton b. X, proton and Z, neutron d. X, electron and Z, proton 2. What is the number of electrons in an atom that has 3 protons and 4 neutrons? a. 1 c. 3 b. 7 d In the late 1800s, experiments using cathode ray tubes led to the discovery of the a. Electron c. Positron b. Neutron d. Proton 4. Which subatomic particles are located in the nucleus of an He-4 atom? a. Electrons and neutrons b. Electrons and protons c. Neutrons and protons d. Neutrons, protons, and electrons 5. What was concluded about the structure of the atom as the result of the gold foil experiment? a. A positively charged nucleus is surrounded by positively charged particles b. A positively charged nucleus is surrounded by mostly empty space c. A negatively charged nucleus is surrounded by positively charged particles d. A negatively charged nucleus is surrounded by mostly empty space 6. Which sequence represents a correct order of historical developments leading to the modern model of the atom? a. The atom is a hard sphere à most of the atom is empty space à electrons exist in orbitals outside the nucleus b. The atom is a hard sphere à electrons exist in orbitals outside the nucleus à most of the atom is empty space c. Most of the atom is empty space à electrons exist in orbitals outside the nucleus à the atom is a hard sphere d. Most of the atom is empty space à the atom is a hard sphere à electrons exist in orbitals outside the nucleus 7. All phosphorous atoms have the same a. Atomic number b. Mass number c. Number of neutrons plus the number of electrons d. Number of neutrons plus the number of protons 7

8 8. Two atoms will always have the same atomic number if they have the same a. Mass number c. Number of neutrons b. Number of protons d. Number of nucleons 9. The atomic mass of an element is the weighted average of the atomic masses of a. The least abundant isotopes of the element b. The naturally occurring isotopes of the element c. The artificially produced isotopes of the element d. The natural and artificial isotopes of the element 10. Which quantity can vary amount atoms of the same element? a. Mass number c. Number of protons b. Atomic number d. Number of electrons 11. What is the mass number of an atom that has six protons, six electrons, and eight neutrons? a. 6 c. 14 b. 12 d An atom that has 13 protons and 15 neutrons is an isotope of the element a. Nickle c. Aluminum b. Silicon d. Phosphorus 13. The total number of protons, electrons, and neutrons in each of four different atoms are shown in the table below Subatomic Particles in Four Different Atoms Atom Total Number of Protons Total Number of Electrons Total Number of Neutrons A D X Z Which two atoms are isotopes of the same element? a. A and D b. A and Z c. X and D d. X and Z 14. Which notations represent different isotopes of the element sodium? a. 32 S and 34 S c. Na + and Na 0 b. S 2- and S 6+ d. 22 Na and 23 Na 15. Which diagram represents the nucleus of an atom of 27 13Al a. 14 n 27 p b. 14 n 13 p c. 27 n 13 p d. 40 n 13 p 8