Lecture 2 - Basic Chemestry

Question 0

What are the four main elements that make up the human body?

Answer 0

oxygen, hydrogen, carbon, nitrogen

Question 1

element

Answer 1

A form of matter indivisible by normal means.

Question 2

compound

Answer 2

Two or more different elements

Question 3

atom

Answer 3

Smallest particles that retain properties of an element

Question 4

Atoms are made of what subatomic particles? What are their respective charges?

Answer 4

protons (positive)
neutrons (neutral)
electrons (negative)

Question 5

Which subatomic particle are represented by atomic numbers?

Answer 5

protons

Question 6

isotope

Answer 6

Atoms of an element with a different number of neutrons, behave the same as the normal element in chemical reactions

Question 7

What determines whether atoms will interact with each other?

Answer 7

The number and arrangement of electrons

Question 8

Properties of electrons

Answer 8

Carry a negative charge
Repel one another
Are attracted to protons in the nucleus
Move in shells (volumes of space surrounding the nucleus)

Question 9

List the number of electrons in the first three shells of an element

Answer 9

First shell: 2
Second shell: 8
Third shell: 8

Question 10

chemical bonds

Answer 10

A union between two atoms

Question 11

valence shell

Answer 11

The outermost shell of an atom.

Question 13

List the three types of bonds, in order of strength, from strongest to weakest

Answer 13

ionic
covalent (either polar or nonpolar)
hydrogen

Question 14

Which bonds are held together by charge differences in elements?

Answer 14

ionic bonds, hydrogen bonds

Question 15

Which bonds are held together by the sharing of electrons?

Answer 15

covalent bonds

Question 16

What is the difference between polar and non-polar covalent bonds?

Answer 16

In polar covalent bonds, the electrons are not shared equally amongst the elements, with electrons spending more time near the larger nucleus, resulting in a charge differential.
In non-polar covalent bonds, the electrons are shared equally, resulting in no charge difference across the element

Question 17

If both ionic and hydrogen bonds are held together by charge differentials, what is the difference between them?

Answer 17

Ionic bonds are created though the exchange of an electron, turning two previously neutral elements into a positive and negative one, strongly attracting each other without sharing electrons.
Hydrogen bonds are created when a polar covalently bonded molecule is attracted to an oppositely charged atom.

Question 18

ionic bond

Answer 18

One atom loses electrons, becoming a positively charged ion, while the atom that gains the lost electrons becomes negatively charged. The charge difference attracts these ions, they do not share the electrons afterwords.

Question 19

hydrogen bond

Answer 19

Atom in one polar covalent bond attracted to oppositely charged atom in another such molecule or same molecule

Question 20

List the properties of water

Answer 20

Cohesive - binds to itself
Adhesive - binds to other
Stabilises temperature
Expands when frozen
Capacity to dissolve substances

Question 21

What are hydrogen ions?

Answer 21

Unbound protons that form when water ionises, a hydrogen wtom with no electron

Question 22

What does pH measure?

Answer 22

The hydrogen ion concentration of a fluid

Question 23

Describe the pH scale

Answer 23

A scale measured between 0 and 14, with 0 being the highest concentration of hydrogen ions and 14 being the lowest, each integer below 14 represents a 10-fold increase in the number of hydrogen ions present.

Question 24

acid

Answer 24

Substances which donate hydrogen ions when dissolved in water, have a pH of < 7

Question 25

base

Answer 25

Substances which accept hydrogen ions when dissolved in water, have a pH of > 7

Question 26

covalent bond

Answer 26

Atoms share a pair or pairs of electrons to fill the valence shell

Question 27

buffer system

Answer 27

A partnership between a weak acid and the base it forms when dissolved, working as a pair to counter shifts in pH, minimising the effects.

Question 28

Identify the reactants and the products of this equation:

2 H2 + O2 -> 2 H2O

Answer 28

H2 and O2 are the reactants, the products are two molecules of water (2 H2O)

Question 29

Why do water molecules form hydrogen bonds?

Answer 29

It is a polar molecule

Question 30

What is an elect called that has lost an electron?

Answer 30

An ion

Question 31

What is an element called that has lost a neutron?

Answer 31

An isotope

Question 32

Why are the noble gas elements so relatively unreactive?

Answer 32

They possess filled valence shells, making their electrons more stable