Ch. 2 - Atoms & Elements

Question 0

What is the Law of Conservation of Mass?

Answer 0

In a chemical reaction, matter is neither created not destroyed.

Question 1

What is matter composed of?

Answer 1

It is composed of small, indivisible particles called ATOMS.

Question 2

What is the Law of Definite Proportions?

Answer 2

All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.

Question 3

What is the Law of Multiple Proportions?

Answer 3

When two elements (A & B) form two different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers.

Question 4

Atomic Theory

Answer 4

1. Each element is composed of tiny, indestructible particles called atoms.
2. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
3. Atoms combine in shape, whole-number ratios to form compounds.
4. Atoms of one element cannot change in to atoms of another element. In a chemical reaction, atoms only change the way they are bound together with other atoms.

Question 5

Electron

Answer 5

A negatively charged, low mass particle present within all atoms.

Question 6

Radioactivity

Answer 6

The emission of small energetic particles from the core of certain unstable atoms.

Question 7

Nuclear Theory

Answer 7

1. Most of the atom’s mass and all of its positive charge are contained in a small core called the Nucleus.
2. Most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed.
3. There are as many negatively charged electrons outside the nucleus as there are positively charged particles (named protons) within nucleus, so that the atom is electrically neutral.

Question 8

Neutrons

Answer 8

Neutral particles within the nucleus. The mass is similar to that of a proton. It has no electrical charge.

Question 9

Atomic Mass Unit

Answer 9

1/12 of a carbon atom containing six protons and six neutrons. The mass of a proton or neutron is approximately 1 amu.

Question 10

Atomic Number

Answer 10

The number of protons in an atom’s nucleus - given the the symbol Z.

Question 11

Isotopes

Answer 11

Atoms with the same number of protons but different number of neutrons.

Question 12

Mass Number

Answer 12

The sum of the number of neutrons and protons in an atom.

Question 13

Cations

Answer 13

Positively charged ions

Question 14

Anions

Answer 14

Negatively charged ions

Question 15

Periodic Law

Answer 15

When the elements are arranged in order of increasing mass, certain sets of properties recur periodically.

Question 16

Metals

Answer 16

• lie on the lower left side and middle of the table
• good conductors of heat and electricity
• can be pounded into flat sheets
• can be drawn into wires
• often shiny
• tend to lose electrons when they undergo chemical changes

Question 17

Nonmetals

Answer 17

• lie on the upper right side of the table
• some are solids at room temperature
• others are liquids or gases
• as a whole they tend to be poor conductors of hear and electricity
• they all tend to gain electrons when they undergo chemical changes

Question 18

Metalloids

Answer 18

• run along the zig zag line

- several are also classified as semiconductors because if their intermediate electrical conductivity