Unit 1: Module 1-Atoms And Reactions

Question 0

Electrons: charge and position in atoms

Answer 0

1) They have a -1 charge.

2) They whizz around the nucleus in orbitals. The orbitals take up most of the volume of the atom.

Question 1

What are atoms made up of?

Answer 1

Protons, neutrons and electrons

Question 2

Where is most of the atom’s mass concentrated?

Answer 2

In the nucleus.

Question 3

Nucleus: size, what you will find in it.

Answer 3

1) The diameter of the nucleus is very small compared to the whole atom.
2) The nucleus is where you’ll find protons and neutrons.

Question 4

Why is a relative mass and relative charge used for subatomic particles?

Answer 4

The mass and charge of these subatomic particles is really small.

Question 5

The relative mass and relative charge of each subatomic particle.

Answer 5

Proton:
-relative mass 1
-relative charge +1
Neutron:
-relative mass 1
-relative charge 0
Electron, e-:
-relative mass 1/2000
-relative charge -1

Question 6

What does the mass number of an element tell you?

Answer 6

This tells you the total number of protons and neutrons in the nucleus.

Question 7

What does the atomic number of an element tell you?

Answer 7

1) This is the number of protons in the nucleus.

2) All atoms of the same element have the same number of protons, so it identifies the element.

Question 8

Why do neutral atoms have no overall charge?

Answer 8

The number of electrons is the same as the number of protons.

Question 9

How can you work out the number of neutrons in an element using the periodic table?

Answer 9

The number of neutrons=mass number-atomic number

Question 10

What is an ion?

Answer 10

Ions have a different number of electrons than protons.

Question 11

Negative ions (e.g. Br-) have ……electrons than protons.

Answer 11

More electrons than protons

Question 12

Positive ions (e.g. Mg^2+)have…….electrons than protons.

Answer 12

Fewer electrons than protons

Question 13

What is an isotope?

Answer 13

Isotopes are atoms of the same element with different numbers of neutrons.

Question 14

What decides the chemical properties of an element?

Answer 14

The number and arrangement of electrons.

Question 15

What decides the physical properties (such as densities and rates of diffusion) of an element?

Answer 15

The mass of the atom (isotopes can have different physical properties)

Question 16

Why do we assume models of atoms are true?

When do we assume they aren’t true?

Answer 16

1) It fits observations and evidence we have at the time.

2) Until someone shows that a model is incomplete or wrong with evidence.

Question 17

What was a problem with the atom model with its electrons arrangement and nucleus?

Answer 17

Electrons in a ‘cloud’ around a nucleus would spiral down into the nucleus, causing the atom to collapse.

Question 18

Niels Bohr’s 4 principles of atoms:

Answer 18

1) Electrons can only exist in fixed orbits, or shells, not between.
2) Each shell has a fixed energy.
3) When an electron moves between shells, electromagnetic radiation is emitted or absorbed.
4) Because the energy of shells is fixed, the radiation will have a fixed frequency.

Question 19

Evaluate the Bohr Model of atoms.

Answer 19

• -The frequencies of radiation emitted and absorbed by atoms were already known from experiments, so the model fitted these observations.
• -The model explained why some elements (the noble gases) are inert. He said that the shells of an atom can only hold fixed numbers of electrons, an elements reactivity is due to its electrons. When an atom has full shells of electrons, it is stable and does not react.