Chemistry

Chapter 2 part 1

Start With Atoms

Element

Atom

Characteristics of Atoms

Characteristics of Atoms

Radioisotopes Radioactive decay• Radioisotopes emit subatomic particles of energy

when their nucleus breaks down, transforming one element into another at a constant rate

• Example: 14C → 14N

PET Scanning

Radioactive Material- Chernobyl and 3 mile Island

Which statement is correct if an isotope of Carbon-14 decayed to form Carbon-12 ?

1. Carbon-14 lost 1 proton

2. Carbon-14 lost 2 protons

3. Carbon-14 lost 1 neutron

4. Carbon-14 lost 2 neutrons

5. Carbon-14 lost 1 electrons

6. Carbon-14 lost 2 electrons

Fig. 2-5a, p. 24

electron

argon 18p+, 18e−

sodium 11p+, 11e–

chlorine 17p+, 17e–

carbon 6p+, 6e– oxygen 8p+, 8e– neon 10p+, 10e–

hydrogen 1p+, 1e– helium 2p+, 2e–

Ion Formation

From Atoms to Molecules

Molecule• Two or more atoms joined in chemical bonds

Compounds• Molecules consisting of two or more elements

3 most common types of bonds in biological molecules are:• Ionic• Covalent• Hydrogen bonds

Ionic Bonds

Chlorine

Sodium

Potassium chloride (KCl) is formed using ionic bonding. Potassium ions have a net positive charge (+1). Chloride ions have a net negative charge (1). How many electrons were in the outer orbital of the potassium (K) and chloride (Cl) atoms?

1. K=7; Cl=72. K=1; Cl=63. K=7; Cl=64. K=1; Cl=7

N has 5 electrons in its outer orbital. How many H can it covalently bond to and have a neutral electrical charge?

1. 2 (NH2)

2. 3 (NH3)

3. 4 (NH4)

4. 5 (NH5)

Fig. 2-10c, p. 28

Water’s Cohesion

H bonds give water cohesion (molecules resist separation)

• Provides surface tension• Draws water up from roots of plants

Why does water display the unique properties we have just discussed?

1. Because of the covalent bonds between the oxygen and hydrogen.

2. Because of its ability to hydrogen bond.

3. Because of its ability to make and break ionic bonds.

4. Because the electrons are shared equally between the oxygen and hydrogen atoms.

Which statement is true when comparing lemon juice (acidic) to baking soda (basic)?

1. Lemon juice has more OH compared to baking soda.

2. Lemon juice has more H+ compared to baking soda.

3. Lemon juice and baking soda both have an equal amount of OH and H+.

4. Baking soda has more H+ when compared to lemon juice.