Chemistry - Unit 1

Question 1

atom

Answer 1

the smallest particle of a chemical element that can exist

Question 2

first model of the atom

Answer 2

John Dalton - The Billiard Ball - 1803

Investigated pressure and experimented the expansion and contraction of gases

Found: Gases are made up of tiny moving spheres. These spheres were solid and indestructible.

Question 3

matter

Answer 3

any substance that has mass and takes up space by having volume

Question 4

second model of the atom

Answer 4

J.J. Thompson - Plum Pudding Model - 1897

Experimented with cathode ray tubes - electrons are accelerated from one end of the tube to another using an electric field

Found: All atoms contain tiny negatively charged subatomic particles (electrons).

Question 5

third model of the atom

Answer 5

Rutherford - Gold foil - 1909

Experiment with gold foil. A piece of gold was hit with alpha particles, which have a positive charge. Most particles went right through, showing that gold atoms were mostly empty space.

Question 6

fourth model

Answer 6

Bohr - The planetary model - 1913

Slightly altered Rutherford’s theory to agree with Planck’s quantum theory (about shells)

Found: Electrons travel in circular orbits around the nucleus.

Question 7

atomic number

Answer 7

the number of protons/electrons

Question 8

atomic mass/mass number

Answer 8

the number of protons and neutrons expressed in AMU

Question 9

electron configuration

Answer 9

the arrangement of electrons in orbitals of an atom written in ?,?,?

Question 10

electron configuration of beryllium-9

Answer 10

2,7

Question 10

identify Li, Ne, Br, H, Na

Answer 10

Lithium, Neon, Bromium, Hydrogen, Sodium

Question 11

group 2

Answer 11

alkaline earth metals - eg. berylium, magnesium, calcium

Question 12

positioning of metals, non-metals and metalloids

Answer 12

metals on left side, non-metals on right side, metalloids are a staircase down to astatine skipping aluminium

Question 12

group 1

Answer 12

alkali metals - eg. hydrogen, lithium, sodium

Question 13

group 3-12

Answer 13

transition metals - eg. magnesium, cobalt, nicklet, copper, zinc

Question 14

group 17

Answer 14

halogens - eg. fluorine, chlorine, bromine, iodine

Question 15

group 18

Answer 15

noble gases - eg. krypton, helium, neon, argon

Question 16

reactivity on the periodic table

Question 17

describe radioactivity

Answer 17

the release of energy from the decay of a nuclei of certain kinds of atoms and isotopes

Question 18

define half-life

Answer 18

the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay

Question 19

define penetrating power

Answer 19

the ability of a certain radiation to penetrate a body

Question 20

define decay

Answer 20

the spontaneous decrease in the number of radioactive atoms in a radioactive material

Question 21

define radioisotope

Answer 21

the unstable form of an element that can emit radiation to transform into a more stable form

Question 22

define isotope

Answer 22

atoms with the same number of protons but different number of neutrons eg. lithium - 6 and lithium - 7

Question 23

three types of radioactive decay

Answer 23

alpha particle, beta particle, gamma radiation

Question 24

describe alpha radiation

Answer 24

• charge = +2
• emits 2 protons and 2 neutrons
• mass = 4 AMU
• Penetrating ability - LOW
• Ionising ability - HIGH
  Stopped by: a few cm of air, thin sheet of paper

Question 25

describe beta radiation

Answer 25

• charge = -1
• emits 1 electron
• mass = 1/1800 AMU
• penetrating ability - MODERATE
• ionising ability - MODERATE
  Stopped by: a few m of air, thin sheet of aluminium

Question 26

describe gamma radiation

Answer 26

• charge = 0 (no charge)
• emits an electromagnetic ray
• mass = 0 AMU
• pentrating ability - HIGH
• ionising ability - LOW
  Stopped by: a thick wall of concrete or lead

Question 27

identify uses of radioisotopes

Answer 27

Radiation in industry:
- Radioactive traces used to detect leaks in underground pipes. Gamma radiation is used to detect an increase in radiation level.
Radiation in agriculture:
- Radioactive phosphorus is used as a tracer to show how well plants are absorbing phosphates
- Gamma radiation can be used to prolong the shelf life of food by killing bacteria.
Radiation in science:
- Uranium dating is used to find the age of rocks. Uranium has a half-life of 4500 million years. Each uranium atom decays into lead. By comparing the the ration of uranium and lead atoms, you can calculate the age of the rock.
Radiation in medicine:
- Cobalt-60 is used in the treatment of cancers. A strong beam of radiation is directed on to the cancerous tissue to kill the cancer cells.