Atoms

Question 1

Greek atom

Answer 1

By Greek philosopher Democritus. Said, if you divided a mass again and again and again, you would end up with an indivisible particle, held together by hooks, called an atomos.

Question 2

John Dalton

Answer 2

Developed an atomic theory: Atoms are tiny particles that make up elements; atoms can’t be divided; all atoms of a given element are the same; atoms of one element are different to all other elements. Developed first table of atomic masses

Question 3

JJ Thompson

Answer 3

Discovered electron using cathode rays (emitted from cathode in cathode-ray tubes). Found cathode rays were a stream of particles with a negative charge, could be deflected by a magnetic and electric field and had a very very small mass. Concluded these particles came from the atoms in the electrode. Proposed plum pudding model.

Question 4

Plum pudding model

Answer 4

Atom is a sea of positive charge, containing negatively charged particles

Question 5

Ernest Rutherford

Answer 5

Proposed nuclear atom model. Geiger and Marsden fired alpha particles at gold foil and measured deflection. Found that they were deflected, disproving plum pudding model. From the deflections measured, Rutherford calculated an atom’s positive charge must be concentrated in the centre.

Question 6

Neils Bohr and others

Answer 6

Proposed that electrons orbited nucleus in shells, otherwise they would spiral into the nucleus. Rutherford discovered the proton in 1918.

Question 7

James Chadwick

Answer 7

Discovered the neutron when bombarding light elements with alpha particles.

Question 8

Mass of an electron

Answer 8

1/2000 the mass of a proton

Question 9

Isotope

Answer 9

Atoms of an element with different numbers of neutrons and different masses

Question 10

Atomic (proton) number

Answer 10

Number of protons in the nucleus of an atom

Question 11

Mass (nucleon) number

Answer 11

Number of particles (protons and neutrons) in the nucleus

Question 12

Ion

Answer 12

Positively or negatively charged atom or (covalently bonded) group of atoms

Question 13

Relative molecular mass or relative formula mass?

Answer 13

RMM for simple molecules; RFM for giant compounds

Question 14

Standard measurement of relative masses

Answer 14

Carbon-12

Question 15

Relative isotopic mass

Answer 15

Mass of an atom of an isotope compared with 1/12 of the mass of an atom of carbon-12

Question 16

Relative atomic mass

Answer 16

The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12

Question 17

RAM=

Answer 17

(sum of RIM x proportion)/total amount of stuff

Question 18

Relative molecular mass

Answer 18

Weighted mean mass of a molecule unit compared with 1/12 of the mass of an atom of carbon-12

Question 19

Relative formula mass

Answer 19

Weighted mean mass of a formula unit compared with 1/12 of the mass of an atom of carbon-12