1. Atoms, Molecules and Ions
Chapter 4

2. Objectives Understand and use the terms ion, cation and anion
Understand the basic set up of the periodic table
Understand the charge of the elements based on their location on the periodic table.

3. Daily Review An atom with two isotopes 78.92 amu, 50.69%
Determine protons, neutron and Electrons.
Calculate the average atomic mass of:
An atom with two isotopes
78.92 amu, 50.69%
80.92 amu, 49.31%

4. Daily Review An atom with two isotopes 78.92 amu, 50.69%
Determine protons, neutron and Electrons.
Calculate the average atomic mass of:
An atom with two isotopes
78.92 amu, 50.69%
80.92 amu, 49.31%
79.91 amu
6 protons, 6 electrons and 8 neutrons

5. REVIEW
Review
Review

6. Dalton’s Atomic Theory (1808)
Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements.
Compounds are composed of atoms of more than one element. The relative number of atoms of each element in a given compound is always the same.
Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed in chemical reactions.
2.1

7. Law of Multiple Proportions2
2.1

8. Law of Conservation of Mass
16 X
8 Y +
8 X2Y
2.1

9. Discovered the Electron!!
J.J. Thomson, measured mass/charge of e-
(1906 Nobel Prize in Physics)
Discovered the Electron!!
2.2

10. Thomson’s charge/mass of e- = -1.76 x 108 C/g
Discovery:
Measured mass of e-
(1923 Nobel Prize in Physics)
e- charge = x C
Thomson’s charge/mass of e- = x 108 C/g
e- mass = 9.10 x g
2.2

11. ERNEST RUTHERFORD
(Uranium compound)
2.2

12. 2.2

13. (1908 Nobel Prize in Chemistry)
particle velocity ~ 1.4 x 107 m/s
(~5% speed of light)
atoms positive charge is concentrated in the nucleus
proton (p) has opposite (+) charge of electron (-)
mass of p is 1840 x mass of e- (1.67 x g)
2.2

14. Rutherford’s Model of the Atom If the atom is the Houston Astrodome
atomic radius ~ 100 pm = 1 x m
nuclear radius ~ 5 x 10-3 pm = 5 x m
If the atom is the Houston Astrodome
Then the nucleus is a marble on the 50 yard line
2.2

15. Chadwick’s Experiment (1932)
H atoms - 1 p; He atoms - 2 p
mass He/mass H should = 2
measured mass He/mass H = 4
a + 9Be
1n + 12C + energy
neutron (n) is neutral (charge = 0)
n mass ~ p mass = 1.67 x g
2.2

16. Subatomic Particles (Table 4.1)
mass p = mass n = 1840 x mass e-
2.2

17. X H H (D) H (T) U Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei
Mass Number X A Z
Element Symbol
Atomic Number H 1
H (D) 2
H (T) 3 U
235 92
238
2.3

18. Isotopes of Hydrogen How many neutrons does each isotope have? Protons
2.3

19. Do You Understand Isotopes?
How many protons, neutrons, and electrons are in C 14 6 ?
6 protons, 8 (14 - 6) neutrons, 6 electrons
How many protons, neutrons, and electrons are in C 11 6 ?
6 protons, 5 (11 - 6) neutrons, 6 electrons
2.3

20. Alkali Earth Metal
Noble Gas
Halogen
Alkali Metal
Period
Group
2.4

21. A diatomic molecule contains only two atoms
A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds H2
H2O
NH3
CH4
A diatomic molecule contains only two atoms
H2, N2, O2, Br2, HCl, CO
A polyatomic molecule contains more than two atoms
O3, H2O, NH3, CH4
2.5

22. cation – ion with a positive charge
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons
2.5

23. A monatomic ion contains only one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4+, NO3-
2.5

24. 2.5

25. How many protons and electrons are in
Do You Understand Ions?
How many protons and electrons are in Al 27 13 ? 3+
13 protons, 10 (13 – 3) electrons
How many protons and electrons are in Se 78 34 2- ?
34 protons, 36 (34 + 2) electrons
2.5

26. Muddiest Point On a sticky note answer:
What did you find most confusing or hard to understand about the lesson?