ATOMIC STRUCTURE: Chapter 4 Atoms and Elements

ATOMIC STRUCTURE: Chapter 4 Atoms and Elements Topics: Atomic Composition Valence Electrons Isotopes-Nuclide Symbols Ion names and Symbols Calculating Atomic Mass Calculating Percent Composition

Standards Addressed:

Atomic and Molecular Structure 1a. Students know how to relate the position of an element in the periodic table to its atomic number and atomic mass. 1b. Students know how to use the periodic table to identify metals, semi-metals {metalloids}, non-metals, and halogens 1e. Students know the nucleus of the atom is much smaller than the atom yet contains most of its mass.

Anticipatory Set:  What are atoms made up of?  Where do you find these particles?

Objectives: By the end of the lesson, the student will:  Know the 3 particles of the atom and where they reside  Know the difference between atomic number and mass number  Know how to write nuclide symbols  Know the three isotopes of hydrogen  Know how to calculate atomic mass  Know how to calculate percent composition  Know how to determine the number of valence electrons  Know how to write ion names and symbols

Purpose: Reason doing lesson. Future purpose. Big picture.  We will use this information to build our chemistry knowledge.  We will use this information as the foundation to calculate limiting reagent problems.  The standardized exams in the spring will test you on this information.

Teacher Input Vocab: Atom- from the Greek atomos=indivisible The atom is the smallest particle of an element that retains the properties of that element.

Nucleus: the center of the atom; composed of neutrons and protons. Because the mass of the proton and the neutron is much larger than that of electrons, almost all the mass is located in the nucleus.

Ion: a charged particle: anion and cation

1 Protons:

Neutrons:

Electrons

Qt: What differentiates one atom from another atom?

Atomic Number (Z): 

(CFU) Qt. What does it mean to be electrically neutral? Qt: What observations can you make about atomic numbers on the periodic table?

(CFU & GP)  What is the atomic number of Chlorine?  What can you tell me about its protons and electrons?  What element has 20 protons?  What is the relationship between the # protons and the atomic number?

(GP) Complete the chart: Element Symbol Atomic Number # Protons Potassium

Qt. What accounts for the mass of the atom?

2 Mass Number (A): 

Qt: What do the atomic number and the mass number have in common?

To find # neutrons:

OR to find mass number:

(GP) Complete the Chart: Atomic # Mass # # Protons # Neutrons # Electrons Chemical Nuclide Nuclide Name Symbol Symbol 9 10

Isotopes: 

A Nuclide Symbol: ZEl A= mass number Z= atomic number Nuclide

 3 # protons # neutrons # electrons Chemical Symbol C [6, 7, 8]

Nuclide Symbol 7

(CFU & GP) Now write the nuclide symbol for the elements in the previous table.

3 Isotopes of Hydrogen Isotope Nuclide # protons # neutrons # electrons of Hydrogen Symbol Protium 1 0 1

Deuterium 1 1 1

Tritium 1 2 1

If you specify the nuclear structure, then you call it a nuclide. But if you say Carbon atom, you do not know which Carbon atom it is, therefore you don’t know how many neutrons it has

Example: brothers and sisters-you are members of the Jones family, but you have not specified 13 which Jones member you are referring to. Jimmy Jones ~ 6C

(CFU & GP) Write the nuclide name and nuclide symbol # protons # neutrons # electrons Nuclide Nuclide Name Symbol 17 20 18

20 20 18

92 146 92

Atomic Mass: 

If you have a recipe, you could count items to put in, say 200 chocolate chips, 3 eggs, etc.

4 But suppose I have a recipe to make a compound. I need 100 hydrogen atoms and 50 oxygen atoms-you cannot count atoms or pluck them out with atomic tweezers! So instead they mass them(weigh them)

Qt. What accounts for the mass of the atom?

12  Know that 1.0 amu is defined as exactly 1/12 the mass of a 6C atom.  Carbon-12 has 6 protons and 6 neutrons, therefore 1 proton or 1 neutron =  Know that 1 amu = 1.6606 x 10 -24 grams  Since the mass mostly depends on # protons and # neutrons, you’d think atomic mass would be a whole number, but it isn’t. How come?

 In nature,

 Relative abundance-

 Sample of carbon from anywhere in the world; coal from S. Africa or W. Virginia, or Pennsylvania → 99% C-12 and 1% C-13

 Atomic Mass of periodic table

 → Idea of weighted average

To Calculate Atomic Mass of an Element To calculate atomic mass you need to know 3 things:

Calculating atomic mass For each isotope of the element:

mass of isotope X relative abundance + mass of isotope X relative abundance….=______amu

Example: Chlorine Calculation Isotope Mass of Isotope Relative Abundance Atomic Mass of Cl Cl-35 34.969 75.77% Cl-37 36.935 24.23%

5 Oh look, that’s the same value on the periodic table

(CFU & GP) How many chlorine atoms actually have a mass of 35.45 amu? So the atomic mass, in amu, is the average of a fictitious non-existent atom of an element.

Example: Copper Calculation Isotope Mass of Isotope Relative Abundance Atomic Mass Cu-63 62.9298amu 69.09% Cu-65 64.9278 30.91% Calculation:

Suppose you are given the mass of the isotopes and the atomic mass of the element and you are asked to calculate the relative abundance of each isotope

To Calculate % Abundance:

Isotope Mass of Isotope Relative Abundance Atomic Mass B-10 10.013 B-11 11.009