Week 1 The Atom

Question 1

What is an atom?

Answer 1

Discrete chemical species comprising of central positively charged nucleus surrounded by negatively charged electrons.
Atoms are always electrically neutral.

Question 2

Law of conservation of mass

Answer 2

There is no detectable change in mass that occurs in chemical reactions. Mass of reactants = mass of products

Question 3

Law of definite proportions

Answer 3

In a given chemical compound, the elements are always combined I’m the same proportions by mass.

Question 4

Define molecule

Answer 4

Collections of atoms with definite structure held together by covalent bonds
Always electrically neutral

Question 5

Define ion

Answer 5

Chemical species with positive or negative charge
Cation - positive. Lost electrons
Anion - negative. Gained electrons

Question 6

What is a compound

Answer 6

Substance containing 2 or > elements in definite and unchanging proportions

Can be comprised of molecules, ions or covalently bonded network of atoms

Question 7

How much of the total volume of an atom does the nucleus occupy?

Answer 7

0.1% of total volume

Question 8

What is an isotope

Answer 8

Atoms of an element that have different numbers of neutrons. I.e. Different mass

Question 9

What are radioactive isotopes?

Answer 9

Unstable nuclei that undergo spontaneous decay to more stable nuclei

Question 10

Define nuclide and radionuclide

Answer 10

Nuclide - any atomic nuclei

Radionuclide - radioactive nuclei

Question 11

What is an atomic mass unit?

Answer 11

1/12 x mass of C-12 atom