Section One: Atoms and Moles

Question 1

What was stated in Dalton’s atomic theory?

Answer 1

• Atoms are tiny particles made of elements (spheres)
• Atoms cannot be divided
• All the atoms in a element are the same
• Atoms of one element are different to those of
  other elements

Question 2

What did Thompson discover about electrons?

Answer 2

• They have a negative charge
• They can be deflected by magnet and
  electric field
• They have very small mass

Question 3

Explain the plum pudding model

Answer 3

• Atoms are made up of negative electrons
  moving around in a sea of positive
  charge

Question 4

What were Rutherford’s proposal after the gold leaf experiment?

Answer 4

• Most of the mass and positive charge of the atom are
  in the nucleus
• Electrons orbit the nucleus
• Most of atom’s volume is the space between the
  nucleus and the electrons
• Overall positive and negative charges must balance

Question 5

Explain the current model of the atom

Answer 5

• Protons and neutrons are found in the nucleus
• Electrons orbit in shells
• Nucleus is tiny compared to the total volume of atom
• Most of atom’s mass is in the nucleus
• Most of the atom is empty space between the nucleus
  and the electrons

Question 6

What is the charge of a proton, neutron, and electron?

Answer 6

P: +1
N: 0
E: -1

Question 7

Which particle has the same mass as proton?

Answer 7

Neutron

Question 8

Which two particles make up most of atom’s mass?

Answer 8

Protons and neutrons

Question 9

What does the atomic number tell about an element?

Answer 9

Atomic number = number of protons in an atom

Question 10

How is mass number calculated?

Answer 10

Mass number = number of protons + number of neutrons

Question 11

How to calculate the number of neutrons?

Answer 11

Number of neutrons = mass number - atomic number

Question 12

Define isotope

Answer 12

Atoms of the same element with different number of neutrons

Question 13

Why does different isotopes of the same element react in the same way?

Answer 13

• Neutrons have no impact on the chemical
  reactivity
• Reactions involve electrons, isotopes have
  the same number of electrons in the same
  arrangement

Question 14

what are ions?

Answer 14

Charged particles formed from the loss or gain of electrons in an atom

Question 15

What is the charge of the ion when electrons are gained? What is the charge of the ion when electrons are lost?

Answer 15

gained: negative
lost: positive

Question 16

Define relative atomic mass

Answer 16

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

Question 17

Define relative isotopic mass

Answer 17

the mass of an atom of an isotope, compared to 1/12th of the mass of an atom of carbon-12

Question 18

ture of false? The relative isotopic mass is same as the mass number

Answer 18

true

Question 19

define relative molecular mass (Mr)

Answer 19

the mean mass of a molecule, compared to 1/12th of the mass of an atom of carbon-12

Question 20

How to calculate the relative molecular mass and relative formula mass?

Answer 20

Both can be calculated by adding the
relative atomic masses of each of the
atom making up the molecule or the
formula

Question 21

What are the uses of mass spectrometry?

Answer 21

• Identify unknown compounds
• Find relative abundance of each isotope of an
  element
• Determine structural information

Question 22

How is the group number related to the number of electrons?

Answer 22

Group number = number of electrons in
the outer shell

Question 23

Which are the 4 elements that don’t tend to form ions and why?

Answer 23

• beryllium, boron, carbon and silicon
• Requires a lot of energy to transfer outer shell
  electrons

Question 24

What are molecular ions?

Answer 24

Covalently bonded atoms that lose or
gain electrons

Question 25

what is the charge of these ions?: ammonium, hydroxide, nitrate, carbonate, sulfate

Answer 25

+1 → NH4 -1 → OH -1 → NO3 -2 → CO3 -2 → SO4

Question 26

how do you find the number of moles from the number of moles from the number of atoms or moles?

Answer 26

no. of moles = number of particles you have ➗ number of particles in a mole (6.02 x 10^23)

Question 27

what formula connects the molar mass of a substance to the number of moles in the substance you have?

Answer 27

no. of moles = mass of substance ➗ molar mass

Question 28

what are the two formulas for working out the number of moles in a volume of gas? (only used at room temp)

Answer 28

no. of moles = volume in dm^3 ➗ 24 OR no. of moles = volume in cm^3 ➗ 24000

Question 29

the ideal gas equation lets you find the number of moles in a certian volume at any temperature and pressure. what is the formula?

Answer 29

pV = nRT p = pressure (Pa) V = volume (m^3) n = no. of moles R = the gas constant ( J K^-1 mol^-1) T = temperature (K)

Question 30

what is the formula for finding out how many moles (or how many grams) of something is dissolved pure 1dm^3 of solution?

Answer 30

no. of moles = (concentration x volume in cm^3) ➗ 1000 OR no. of moles = concentration x volume in dm^3