Atomic Structure And Isotopes

Question 1

What was stated in Dalton’s Atomic theory?

Answer 1

Atoms are tiny particles made of elements
Atoms cannnot be divided
All the atoms in an 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 a very small mass

Question 3

Explain the plum pudding model

Answer 3

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

Question 4

What was Rutherford 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 the atoms volume is in the space between the electrons and the nucleus
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 the atom
Most of the atoms 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

Proton is +1
Neutron is 0
Electron is -1

Question 7

What particle has the same mass as a proton?

Answer 7

Neutron and they have a mass of 1

Question 8

What is the mass of an electron?

Answer 8

1/1836

Question 9

Define isotope

Answer 9

Atoms of the same element with different number of neutrons.

Question 10

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

Answer 10

Neutrons have no impact on chemical reactivity

Reactions involve electrons, isotopes have the same number of electrons in the same arrangement.

Question 11

What are ions?

Answer 11

Charged particles that are formed when an atom loses or gains electrons.

Question 12

What are the charges of a) an atom that has gained electrons. And b) an atom that loses its electrons

Answer 12

a) negative, an anion

b) positive, a cation

Question 13

What is the unit used to measure atomic masses called?

Answer 13

Unified atomic mass unit, u

Question 14

Define relative atomic mass

Answer 14

The weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon-12

Question 15

What is the unit of relative atomic mass

Answer 15

No units

Question 16

Define relative isotopic mass

Answer 16

The mass of a atom of an isotope compared with one twelfth of the mass of an atom of carbon-12

Question 17

What two assumptions are made when calculating mass number?

Answer 17

Contribution of the electron is neglected

Mass of both neutron and proton is taking as 1

Question 18

What are the uses of mass spectrometry?

Answer 18

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

Question 19

How does a mass spectrometer work?

Answer 19

The sample is made into positive ions
They pass through the apparatus and are separated according to mass to charge ratio
A computer analyses the data and produces a mass spectrum.

Question 20

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

Answer 20

Group number= number of electrons in the outer shell.

Question 21

Do metals usually gain or lose electrons?

Answer 21

Lose electrons

non-metals generally gain electrons

Question 22

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

Answer 22

The elements are beryllium, boron, carbon and silicon.

As it requires a lot of energy to transfer outer shell electrons.

Question 23

What are molecular ions?

Answer 23

Covalently bonded atoms that loses or gain electrons.

Question 24

What is the charge of an ammonium ion?

Answer 24

+1 —> NH4 +

Question 25

What is the charge of a hydroxide ion?

Answer 25

-1 —> OH-

Question 26

What is the charge of a nitrate ion?

Answer 26

-1 —> NO3-

Question 27

What is the charge of a carbonate ion?

Answer 27

-2 —> CO3 2-

Question 28

What is the charge of a sulphate Ion?

Answer 28

-2 —> SO4 2-

Question 29

What is an empirical formula?

Answer 29

Simplest whole number ratio of atoms of each element present in a compound

Question 30

How to calculate empirical formula?

Answer 30

Divide the amount of each element by its molar mass
Divide the answers by the smallest value obtained
If there is a decimal, divide by a suitable number to make it into a whole number.