Atoms and Periodic Table. P.29 in ILL September 9, 2011

Transcription

1 Atoms and Periodic Table P.29 in ILL September 9, 2011

2 Atoms All matter is comprised of elements which are made up of atoms. This means atoms are the building blocks of matter. The structure of the atom is a nucleus (at its center), an electron cloud (surrounding the nucleus) and its valence shell (outermost energy level).

3 Atoms The nucleus has subatomic particles called protons and neutrons Protons positively charged Neutrons no charge/neutral The protons and neutrons make up most of the atom s mass The electron cloud is filled with electrons Electrons negatively charged Electrons are infinitely small much smaller than a proton or neutron

4 Atoms The valence shell has valence electrons Determine the chemical properties of the element Determine the stability of the atom Determine how reactive (likely to combine) the atom is Only electrons involved with bonding 8 is the magic number meaning if there are 8 valence electrons, the atom feels stable and does not want to react with any other atom (exception: hydrogen and helium which only need 2 for stability)

5 Atoms Valence shell

6 Periodic Table The elements are arranged in the periodic table They are arranged by increasing atomic number and atomic mass (weight) Each element is given an atomic symbol The table is in a geometric pattern (periods and groups) designed to show patterns in the properties of the elements.

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8 Atomic Symbol A symbol (one or 2 letters) that represents either the name of the element or the Latin name of the element.

9 Atomic Number The amount of protons, which is also equal to the number of electrons in each atom of the element.

10 Atomic Mass/Weight The mass of one atom of that element. This value can be used to find the number of neutrons in the atom by using the following equation: Atomic Mass Atomic Number = # of Neutrons **Always round the atomic mass to nearest whole number!!**

11 Practice, Practice how many of each? Protons= Neutrons= Electrons= Protons= Neutrons= Electrons=

12 Period Each row of the periodic table represents a period As you move from left to right within each period, the atomic mass increases as does the number of protons (atomic number) Also, the valence shells of the atoms fill with electrons, with one additional electron for each step to the right (exception: transition metals)

13 Group/Family Each column of the periodic table is called a group (aka family) and numbered 1 18 Each group/family is given a name to indicate the elements in that group share the same characteristics and behave the same way

14 Group/Family Elements of the same group have the same number of valence electrons (exception: transition metals) From left to right, the number of valence electrons increases by 1 (skipping the transition metals) A full outer energy level would have 8 valence electrons in it (= stable). The only exception is for period 1 any idea why?

15 Ions Ions are atoms that have an overall charge because they have gained or lost valence electrons. Positive ions are those that lose an electron and therefore have more protons (+). Negative ions are those that gain an electron and therefore have more electrons (-).

16 Isotopes The atomic mass on the periodic table is really an average of all the possible masses ever discovered for that atom The reason the mass is not always the same is because for some atoms, there will be more or less neutrons For example, chlorine is supposed to have 18 neutrons but some chlorine atoms have 20 making it an isotope

17 Color Code your Periodic Table! Using pg D20-21 (in textbook) as a guide, color code your periodic table so that it shows the following: metals, nonmetals, metalloids (you chose your own colors) Make sure you darken your metalloid stair steps!! Create a color key and follow teacher s instructions for making it a cheat sheet for determining valence electrons

18 Put your table to work How many valence electrons for phosphorus (P)? What is the symbol for magnesium? What is the atomic mass of copper (Cu)? How many protons does silicon (Si) have? How many total electrons for carbon (C)? How many neutrons in iron? What state of matter is bromine at room temp? Is calcium a metal or non-metal? How did you do?