Chapter 2 (Chemical)

Question 1

Matter

Answer 1

Elements

Compounds

Question 2

Elements

Answer 2

Currently 118
92 naturally occurring
26 man-made

Essential
No life without them
Carbon

Trace
Need a little of them
Copper

Question 3

Compounds

Answer 3

Made of more than one atom

Same of different element

Question 4

Properties of Elements

Answer 4

Each element consists of unique atoms

An atom is the smallest unit of matter that still retains the properties of an element and is composed of subatomic particles
Neutron
Proton
Electron

Question 5

Atomic Number

Answer 5

Number of protons in its nucleus

Question 6

Atomic Mass

Answer 6

Atom’s total mass
4 daltons

Approximated by the sum of protons and neutrons in the nucleus

Question 7

Neutron Mass and Proton Mass are measured in…

Answer 7

Daltons

Question 8

Energy Levels of Electrons

Answer 8

Circle the nucleus and are negatively charged
Stabilize the positive charge of the nucleus
An equal number of electrons and protons will give a net charge equal to neutral (Noble Gases)

Electrons orbit the nucleus in “shells” or “orbitals”

Question 9

Isotopes

Answer 9

Some elements have more neutrons than other atoms of the same element
Have greater mass

Stable and unstable isotopes
Carbon

Carbon 12 – 12C, 6 protons/6 neutrons
Carbon 13 - 13C, 6 protons/7 neutrons
Carbon 14 - 14C, 6 protons/8 neutrons

12C and 13C are stable, 14C is unstable (radioactive)

Question 10

The chemical behaviour of an atom is mostly determined by the…

Answer 10

Valence electrons (outer shell)

Question 11

Elements with a full valence shell are…

Answer 11

Chemically inert

Question 12

Chemical bonds

Answer 12

Interactions usually result in atoms staying close together, held by attractions

Question 13

Types of Chemical Bonds (3)

Answer 13

1. Covalent Bonds
2. Ionic Bonds
3. Hydrogen Bonds

Question 14

Covalent Bonds

Answer 14

Common
Very strong

Covalent bonds form when atoms share pairs of valence electrons

Found in many compounds, especially those that contain carbon

A single covalent bond (single bond) is the sharing of one pair of valence electrons

A double covalent bond (double bond) is the sharing of two pairs of valence electrons

Question 15

Ionic Bonds

Answer 15

Moderately strong

A cation is a positively charged ion (cats are good)

An anion is negatively charged ion (onions are bad because they make you cry)

An ionic bond is an attraction between an anion and a cation

Question 16

Hydrogen Bonds

Answer 16

Weak
Electron density

Occur between covalently bonded molecules that display polarity
When hydrogens are bonded to oxygen, the larger oxygen atom tends to pull the electrons closer to itself

Creates a region with partial negative charge (O)

And a region with partial positive charge (H)
The water molecule H2O

These regions can now participate in hydrogen bonding

Question 17

Hydrogen Bonding

Answer 17

Loose attraction between oppositely charged regions of different molecules
In water (H2O) the H’s of one molecule are attracted to the O’s of other molecules

In living cells, the electronegative partners are usually oxygen or nitrogen atoms

Question 18

Hydrophobic Forces

Answer 18

Molecules can be described as polar or non-polar

Polar and non-polar substances repel from each other

Polar substances are attracted based on (+ / -) charges
Ionic and Hydrogen Bonds
Hydrophilic (likes water)

Non-polar substances are unable to hydrogen bond with water and thus are unable to interact with water
They actually repel it
Hydrophobic