Terms in Chem

Question 1

Relative atomic mass (Ar)

Answer 1

the weighted average mass of naturally occurring atoms of an element on a scale where an atom of carbon-12 has a mass of exactly 12 units

Question 2

Relative isotopic mass

Answer 2

the mass of a particular atom of a particular isotope of an element on a scale where an atom of carbon-12 has a mass of exactly 12 units

Question 3

Relative molecular mass (Mr)

Answer 3

the relative mass of one molecule of the compound on a scale where the carbon-12 isotope has a mass of exactly 12 units

Question 4

Relative formula mass (Mr)

Answer 4

the mass of 1 formula unit of a compound measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units

Question 5

Avogadro constant (Na or L) and number

Answer 5

The number of atoms, molecules, ions or other entities in one mole of a substance. The Avogadro constant is equal to 6.02 x 10^23

Question 6

mole

Answer 6

the amount of a substance that has the same number of specific particles (atoms, molecules, or ions) as there are atoms in exactly 12 g of the carbon-12 isotope

Question 7

Molar mass

Answer 7

the mass of a mole of a substance

Question 8

Avogadro’s constant

Answer 8

the number of atoms in a mole of atoms (6.02 x 10^23 atoms)

Question 9

Isotope

Answer 9

atoms of the same element (same number of protons) with different numbers of neutrons

Question 10

Molecular formula

Answer 10

A formula which shows the number of atoms of each element in a molecule

Question 11

Anhydrous

Answer 11

Anhydrous salts are the compounds left after removing the water from a hydrated salt. Anhydrous means ‘without water’

Question 12

Hydrated

Answer 12

Contains water

Question 13

Acid

Answer 13

A Proton Donor

Question 14

Base

Answer 14

A Proton acceptor

Question 15

Alkali

Answer 15

A soluble base

Question 16

Oxidation state

Answer 16

The states of oxidation or reduction shown by an element in its chemistry

Question 17

First ionization energy

Answer 17

The energy required to remove 1 electron from every atom in 1 mole of gaseous atoms to form a mole of gaseous 1+ ions
X –> X^+ + e^–

Question 18

Electron Orbital

Answer 18

a subdivision of a sub shell and shell. Each orbital is defined by its energy, shape and direction in space. Each orbital contains up to two electrons.

Question 19

Electron Shell

Answer 19

An energy level representing the distance of a group of electrons from the nucleus of an atom.

Question 20

Ionic bond

Answer 20

A bond formed by the electrostatic forces of attraction between a positively charged ion and a negatively charged ion

Question 21

Dative covalent bond

Answer 21

A bond formed when one atom contributes both electrons in a covalent bond ( forms a shared pair of electrons)

Question 22

covalent bond

Answer 22

A bond formed by the attraction between positive charges in the nuclei and the negative charge on the shared electron pair.

Question 23

Electronegativity

Answer 23

The measure of the pull of an atom on a pair of electrons in a chemical bond

Question 24

Permanent dipole

Answer 24

An intermolecular force between two polar molecules