Ch. 2 The chemistry of life.

Question 1

**What is an element?

Answer 1

A substance that can’t be broken down into simpler chemical substances.

Question 2

What four elements make up 96% of the mass of the human body?

Answer 2

H, O, N, C

Question 3

What are the other common elements?

Answer 3

Ca, P, K, S, Na, Cl, Mg

Question 4

What are trace elements?

Answer 4

4% - elements that play a vital role in healthy cells.

Question 5

**What is an atom?

Answer 5

The smallest particle of an element that has the characteristics of an element.

Question 6

The center of an atom is the ______?

Answer 6

Nucleus

Question 7

The nucleus if made up of _____ which are ______ charged and ____ which are neutral.

Answer 7

Protons, positively charged, neutrons.

Question 8

Elements are arranged the Periodic Table according to the?

Answer 8

Number of protons they have. This number is called the atomic number.

Question 9

The region of space surrounding the nucleus contains extremely small, ______ particles called ________.

Answer 9

Negatively charged, electrons.

Question 10

The region of space surrounding the nucleus is also knows as?

Answer 10

The electron cloud.

Question 11

**Within the electron cloud, there are energy levels or _____ which the electrons move around.

Answer 11

Valences

Question 12

What are isotopes?

Answer 12

Atoms of the same element that have the same number of protons and different number of neutrons. E.g., Carbon - 12 naturally occurring.

Question 13

Carbon - 14 (2 more neutrons)?

Answer 13

Radioactive nucleus, unstable, gives off radiation.

Question 14

**What is a compound?

Answer 14

Atoms of two or more elements chemically combine.

Question 15

For many elements, at atom becomes _____ when its ______ energy level is full. (either _____ or _____ electrons)

Answer 15

Stable, outer, 2,8

Question 16

**What is a covalent bond?

Answer 16

The force between two atoms that share an electron pair.

Question 17

The electrons being shared in a covalent bond _______ holding them close together.

Answer 17

Move around both elements.

Question 18

**Molecules are?

Answer 18

A group of atoms held together by a covalent bond.

Question 19

**What is an ionic bond?

Answer 19

The attractive force between two ions of a positive charge.

Question 20

**What is an ion?

Answer 20

A charged atom that gains or loses electrons. If there are more protons it is positively charges. If there are more electrons it is negatively charged.

Question 21

Ionic bonds are _____ abundant in living things than covalent molecules, but ions are important __________.

Answer 21

Less, in biological processes. E.g, NA + and K + pumps conduct nerve impulses.

Question 22

**What is a valence electron?

Answer 22

The electrons in the outer most shell that are gained or lost in a chemical reaction.