Chemistry - Atomic Theory

Question 1

what is an atom?

Answer 1

the smallest unit of matter that can exist by itself. atoms may be held together by chemical bonds to form molecules

Question 2

what does each atom contain?

Answer 2

a central nucleus with electrons orbiting in spheres

Question 3

what are subatomic particles?

Answer 3

the particles that make up atoms in matter. refer to atomic history to find out about their info.

Question 4

what are protons?

Answer 4

a particle with a positive charge, the electric charge of a proton is exactly equal and opposite to an electron

Question 5

what are electrons?

Answer 5

negative charge, electric charge is equal and opposite of a proton

Question 6

what are neutrons?

Answer 6

no charge, neutrons weigh the same as protons

Question 7

what are the properties of atoms?

Answer 7

element
atomic weight
mass number
atomic number

Question 8

what is an element?

Answer 8

substance consisting atoms of the same kind, a element cannot be changed into the other by splitting atoms

Question 9

what is atomic weight?

Answer 9

mass of an atoms of the element relative to carbon 12

Question 10

what is the mass number?

Answer 10

number of protons plus no. of neutrons

Question 11

what is the atomic number?

Answer 11

no. of protons in an atom (also indicates the number of electrons if the atom is neutral)
see properties practice table lesson 5

Question 12

what is atomic theory?

Answer 12

ideas and models put forward throughout time to showcase the structure of the atom

Question 13

what are the 5 atom models and who created each of them?

Answer 13

solid sphere model - john dalton
plum pudding model - j.j thomson
nuclear model - ernest rutherford
planetary model - niels bohr
quantum model - erwin schrondinger (move in waves not like the planetary way)

Question 14

what is half life?

Answer 14

measurement of the time it takes for a given amount of the substance to become reduced by half as a consequence of decay, resulting in the emission of radiation

Question 15

what is radioactivity?

Answer 15

breakdown or decay of unstable substances eg uranium or plutonium - release radiation in the form of alpha or beta particles or nuclear energy in the form of gamma rays

Question 16

describe alpha particles

Answer 16

have double the positive charge with 2 neutrons and is slow moving and can only penetrate at a short distance.

Question 17

describe beta particles

Answer 17

are electrons that are emitted from a radioactive nucleus. it has a high velocity and can penetrate further than an alpha particle. a stream of beta particles form a beta ray.

Question 18

describe gamma particles

Answer 18

are highly penetrating radiation belonging to the electromagnetic spectrum and have no charge

Question 19

what are radioactive isotopes and what are they used for?

Answer 19

an isotope that is radioactive (hydrogen - 3, carbon 14) they are used for
- labels to trace the movement of elements during chemical reactions and complex biological pathways
- in industry to locate leaks in pipes and to monitor thickness of and flaws in materials
- in medical procedures (locate brain tumours, monitor the functioning of organs)
- as a source of gamma rays for the treatment of cancer, sterilising medical supplies, controlling insect pests and preserving food

Question 20

what are isotopes? how do we solve them?

Answer 20

when atoms have the same no. of protons but different no. of neutrons. a = b (x) + c (1 - x). In the equation, “a” is the average atomic mass, “b” is the atomic mass of one isotope, “c” is the atomic mass of the other isotope, and “x” is the abundance of the first isotope.

Question 21

why are electrons important and how many does each shell hold?

Answer 21

allow for different types of bonding (ionic or covalent) to occur between different elements

electrons are contained within shells which is the space or sphere which an electron travels around the nucleus of an atom. each shell corresponds to a different energy level.

shell 1 -2
shell 2 - 8
shell 3 - 8
shell 4 - 18