C2 Atoms, ions and compounds

Question 1

what is the mass and charge of an electron?

Answer 1

1/1836th the mass of a proton
- negative charge

Question 2

mass and charge of a proton?

Answer 2

1, 1+

Question 3

list facts about the atom

Answer 3

-mass of atom is concentrated in the nucleus
-equal proton and electron number means atom is neutral
-total positive charge cancelled by total negative charge
-most atoms have slightly more neutrons than protons
-as the nucleus gets larger, more neutrons are added

Question 4

define atomic number

Answer 4

number of protons in atoms of an element

Question 5

define isotope

Answer 5

atoms of the same element with different numbers of neutrons and different masses. most elements are made up of a mixture of isotopes

Question 6

describe relationship between isotopes and chemical reactions

Answer 6

-different isotopes of the same element have the same number of electrons
-neutron number has no effect on element reactions
so different isotopes of an element reach in the same way

Question 7

define ion

Answer 7

charged atom.
cation - positive ions, atoms with less electrons than protons
anion - negative ions, atoms with with more electrons than protons

Question 8

define relative atomic mass

Answer 8

weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 9

define relative isotopic mass

Answer 9

weighted mean mass of an isotope of an element relative to 1/12th of the mass of an atom of carbon-12

Question 10

define weighted mean mass

Answer 10

takes into account:
-percentage abundance of each isotope
-relative isotopic mass of each isotope

Question 11

how is relative atomic mass determined?

Answer 11

-found experimentally with a mass spectrometer

1. sample placed in mass spectrometer
2. sample vaporized then ionized to form positive ions
3. ions are accelerated. heavier ions move more slowly and are harder to deflect than lighter ions, so ions of each isotope are separated
4. ions are detected on a mass spectrum as a mass-to-charge ratio m/z.
5. each ion that reaches the detector adds to the signal, so the greater the abundance, the larger the signal

Question 12

state the number of protons, neutrons and electrons in a chromium 3+ ion.

Answer 12

21 electrons
29 neutrons
24 protons

Question 13

define relative molecular mass

Answer 13

The ratio of the average mass per molecule of the naturally occurring form of an element or compound to 1/12 of the mass of a carbon–12 atom.

Question 14

define relative formula mass

Answer 14

relative masses of ionic compounds or ions

Question 15

how to calculate relative atomic mass from mass spectrum results below :
75.78% of chlorine-35
24.22% of chlorine-37

Answer 15

relative atomic mass:
(75.78 x 35) + (24.22 x 37) / 100

=35.4844 = 35.5 (1.d.p)

Question 16

what two ions does copper form

Answer 16

Cu+ and Cu2+

Question 17

what two ions does iron form

Answer 17

Fe2+ and Fe 3+

Question 18

what is a binary compound?

Answer 18

-contains two elements only
- ending of second elements to -ide
-for ionic compounds, metal ion comes first

Question 19

define polyatomic ions

Answer 19

ions containing atoms of more than one element bonded together

Question 20

formula of an ammonium ion

Answer 20

NH4+

Question 21

nitrate ion?

Answer 21

NO3-

Question 22

Nitrite ion?

Answer 22

NO2-

Question 23

hydrogencarbonate?

Answer 23

HCO3-

Question 24

manganate (VII)

Answer 24

MnO4-

Question 25

sulfite ion?

Answer 25

SO3 2-

Question 26

dichromate (VI)

Answer 26

Cr2O7 2-

Question 27

sulfate ion?

Answer 27

SO4 2-

Question 28

phosphate ion?

Answer 28

PO4 3-