Atomic Structure

Question 1

Who put forth the first notion of atoms? When?

Answer 1

Around 400 B.C. Democritus stated that matter is made up of tiny particles.

Question 2

When and who discovered the Electron?

Answer 2

JJ Thomson discovered the electron in 1897.

Question 3

When and who discovered the proton and nucleus?

Answer 3

Ernest Rutherford discovered the nucleus and proton in 1911.

Question 4

When and who discovered the Neutron?

Answer 4

James Chadwick discovered the neutron in 1932.

Question 5

Who proposed the Plum Pudding Model? When? What is it?

Answer 5

JJ Thomson proposed the Plum Pudding Model in 1897.

The Plum Pudding Model is a positive matrix with negative particles embedded inside.

Question 6

Draw and Label the Plum Pudding Model.

Answer 6

LABELS:

1. Title.
2. Positively Charged.
3. Negatively Charged.

Question 7

What kind of Model did Rutherford propose? Explain? When?

Answer 7

1911 - Rutherford’s model compared the atom to the solar system, where negatively charged electrons orbit a positively charged nucleus.

Question 8

What did Neils Bohr do? When?

Answer 8

In 1913 Neils Bohr stated that electrons are in fixed objects or “shells” at different distances from the nucleus of the atom.

Question 9

How did Chadwick update Rutherford’s Atomic Model? When?

Answer 9

In 1932 Chadwick updated the model. The central nucleus is now made up of positively charged protons and electrically neutral neutrons and is surrounded by electrons orbiting in “shells” different distances away.

Question 10

What is today’s model of the atom?

Answer 10

The central positively charged nucleus containing protons and neutrons is surrounded by orbiting electrons in shells.

Question 11

What are the differences between the Plum Pudding model and Today’s Model of the atom?

Answer 11

The Plum Pudding model states that there are stationary negative charges embedded within a positive matrix.

Whilst in today’s model:

1. The electrons are not stationary - but orbit the nucleus in shells.
2. The nucleus is made up of protons (which are positive in charge) and neutrons (which are neutral in charge).
3. The atom is mostly made up of empty space.

Question 12

What is the relative charge, relative mass and location of protons, neutrons and electrons?

Answer 12

Protons have a relative charge of +1, a relative mass of 1 and are located in the nucleus.

Neutrons have a relative charge of 0, a relative mass of 1 and are located in the nucleus.

Electrons have a relative charge of -1, a relative mass of 1/1840 and they orbit around the nucleus.

Question 13

What is an atom?

Answer 13

An atom is the smallest particle of an element that can exist on its own yet still be recognised as that element.

Question 14

What is an ion?

Answer 14

An electrically charged particle formed when an atom gains or loses electrons.

Question 15

What is cation?

Answer 15

A cation is a positively charged ion formed when an atom loses an electron or electrons.

Question 16

What is a molecule?

Answer 16

A molecule is a particle made from two or more atoms covalently bonded.

Question 17

What is an atomic number?

Answer 17

The atomic number is the number of protons in the nucleus of the atom.

Question 18

What is the mass number?

Answer 18

The mass number is the total number of protons and neutrons in the nucleus of an atom.

Question 19

How can you calculate the number of neutrons in an atom using the mass and atomic number?

Answer 19

You subtract the atomic number from the mass number.

Mass number - Atomic number = Number of neutrons.

Question 20

Why do atoms have no overall charge despite containing charged particles?

Answer 20

Atoms have no overall charge because the number of protons (positively charged particles) is equal to the number of electrons (negatively charged particles). Thus, their unlike charges cancel each other out making the overall charge of the atom neutral.

Question 21

How many electrons can fit in the first electron shell?

How many electrons can fit in the second electron shell?

How many electrons can fit in the third electron shell before a fourth one is started?

Answer 21

The first electron shell can fit two electrons.

The second electron shell can fit eight electrons.

The third electron shell can fit eight electrons before a fourth electron shell is started.

Question 22

Zinc has 30 electrons, write this in electronic configuration.

Answer 22

2,8,8,8,4

Question 23

What is 1 nanometre in standard form in metres?

Answer 23

1 nanometre = 1 X 10⁻⁹.

Question 24

What is 1 picometre in standard form?

Answer 24

1 picometre = 1 X 10⁻¹².

Question 25

What is one femtometre in standard form?

Answer 25

1 femtometre = 1 X 10⁻¹⁵.

Question 26

What is the typical radius of an atom?

Answer 26

An atom is typically 0.1 nanometres or 100 picometres.

Question 27

What is the typical radius of the nucleus?

Answer 27

The radius of the nucleus is approximately 10 femtometres OR 1/10,000 of the particular atom.

Question 28

What is the definition of an isotope?

Answer 28

Isotopes are atoms of an element with the same atomic number but a different mass number, indicating a different number of neutrons.

Question 29

What is the difference between Chlorine-35 and Chlorine-37?

Answer 29

Chlorine-37 is an isotope with two more neutrons than Chlorine-35.

Question 30

How do you calculate the relative mass of elements using their abundances and isotopes? Calculate the relative atomic mass of Chlorine knowing that the abundance for Chlorine-35 is 75% and the abundance for Chlorine-37 is 25%.

Answer 30

The relative atomic mass of an element = (atomic number of first isotope X its abundance) + (atomic number of its second isotope X its abundance)

The relative atomic mass of Chlorine = (35 X 75/100) + (37 X 25/100) = 35.5

Question 31

How do chemical and physical properties differ throughout isotopes? For example, what is the difference between Chlorine-35 and Chlorine-37?

Answer 31

Isotopes do not differ in electronic structure - hence their chemical properties (chemical properties like reactivity, etc) stay the same throughout isotopes (of the same element).

Isotopes do differ in their numbers of neutrons - since neutrons do not contribute to the atom in charge but in mass, hence why the physical properties (boiling and melting points, etc) differ throughout isotopes (of the same element.

Chlorine-37 has two more neutrons than Chlorine-35 - meaning that Chlorine-37 is slightly heavier than Chlorine-35 and has a slightly higher boiling point.

Question 32

What kind of ions do metals form when reacting?

How do their naming conventions change once an ion has been formed?

Answer 32

Metals (generally) form positive ions - cations.

Metals don’t change their names once they have become ions.

Question 33

What kind of ions do non-metals form?

How do their naming conventions change once they have formed into an ion?

Answer 33

Non-metals form negative ions - anions (most of the time).

Non-metals form “ides” once they become ions.

Question 34

What is an element?

Answer 34

An element is a single pure substance that cannot be broken down into anything simpler by chemical means.

Question 35

What is a compound?

Answer 35

A compound is a single pure substance made from two or more elements chemically combined.