Unit 1 - Matter & Chemical Trends, and Chemical Bonding

Question 1

Matter

Answer 1

Matter consists of pure substances and mixtures

Question 2

Pure Substances

Answer 2

Pure substances consist of elements (ex: oxygen) and compounds (ex: water)

Question 3

Mixtures

Answer 3

Mixtures can be classified as:

• Homogeneous
• Heterogeneous
• Mixtures can be separeted into their components (pure substances), by physical means.

Question 4

Compounds

Answer 4

in a compound, atoms are bounded chemically, therefore, they can only be separated into its constituent elements through a chemical reaction.

Question 5

Homogeneous

Answer 5

Visibly indistinguishable components; also known as a solution; has uniform composition throughout.

Question 6

Heterogeneous

Answer 6

Visibly distinguishable components

Question 7

Distillation

Answer 7

Distillation is a process that depends on differences in the volality of the components; this method is ideal for separating a liquid from a solid in a homogeneous mixture. It is also a good methods for separating a homogeneous mixture of 2 liquids as long as their boiling points are not too close.
(Note: volality - the tendency of a substance to vaporize)

Question 8

Filtration

Answer 8

Filtration is a method of separating a solid from a liquid in a heterogeneous mixture.

Question 9

Chromatography

Answer 9

Chromatography is a separation method using a mobile phase and a stationary phase.

Question 10

Paper Chromatography

Answer 10

A simple type of chromatography which uses a strip of porous paper, such as filter paper, as the stationary phase.

Question 11

Where does the term “atom” come from? What does it mean?

Answer 11

Atom comes from the Greek word “atomos” meaning indivisible

Note: indivisible - unable to be divided or separated

Question 12

Dalton’s Atomic Theory

Answer 12

-All matter is made up of small particles called atoms. An atom cannot be divided into smaller particles.
-The atoms of one element have the same properties, such as mass and size. These properties are different from the properties of the atoms of any other element.
-Atoms of different elements combine in specific proportions to form compounds. (Ex: 2 atoms of hydrogen combine with one atom of oxygen to form water; law of conservation of mass)
-In chemical reactions, atoms are not changes; rather, they are reorganized (Law of conservation of mass).
(Note: we now know that atoms can be broken down further into subatomic particles)

Question 13

Thomson’s Atomic Model (The Plum Pudding Model)

Answer 13

He assumed that an atom consisted of a diffuse cloud of positive charge with the negative electrons embedded randomly in it.

Question 14

Rutherford’s Atomic Model

Answer 14

He performed a series of experiments to test Thomson’s model. He reasoned that if Thomson was correct, the positive alpha particles should travel through the sheet with very minor deflections in their path. However, the results were different than he expected! Most of the alpha particles passed through as he anticipated, but many were deflected at large angles and some were reflected never hitting the detector. He reasoned that the large deflection of the alpha particles could only be caused by a center of concentrated positive charge that contains most of the atom’s mass.

Question 15

Bohr’s Atomic Model

Answer 15

He stated that the electron in a hydrogen atom moves around the nucleus only in certain allowed circular orbits.
(Note: Quantum scientist indicated that although electrons do move in certain allowed regions around the nucleus called “energy levels”, the path is not circular. We can’t actually know the exact position of an electron at each instant while it is moving.)

Question 16

Electron

Answer 16

Mass (kg): 9.109 x 10^-32
Relative Charge: -1
Relative Position: surrounding the nucleus
(Note: the number of electrons is the same as the number of protons for a neutral atom!!)

Question 17

Proton

Answer 17

Mass (kg): 1.673 x 10^-27
Relative Charge: +1
Relative Position: nucleus
(Note: the number of protons determines the identity of the atom!!)

Question 18

Neutron

Answer 18

Mass (kg): 1.675 x 10^-27
Relative Charge: 0
Relative Position: nucleus

Question 19

Atomic Number (Z)

Answer 19

The number of protons in an atom, it is written as a subscript in the element symbol

Question 20

Mass Number (A)

Answer 20

The total number of protons and neutrons in an atom, it is written as a superscript in the element symbol

Question 21

Element Symbol

Answer 21

^AXZ

Note: where A is a superscript, Z is a subscript, and X is the element!

Question 22

Isotopes

Answer 22

Atoms with the same number of protons but different number’s of neutrons

Question 23

Group or Family

Answer 23

A vertical column in the periodic table is called a group or family

Question 24

Period

Answer 24

A horizontal row is called a period

Question 25

Alkali Metals

Answer 25

The elements of group 1A, with the exception of hydrogen

Note: the word “alkali” means “basic”, and these metals form basic compound upon reaction with water

Question 26

Alkali Earth Metals

Answer 26

The elements of group 2A; they not only form basic compounds upon reaction with water, but they are also found in high abundance in the earth’s crust.

Question 27

Halogens

Answer 27

The elements of group 7A

Note: the word “halogen” means “salt maker”

Question 28

Noble Gases

Answer 28

The elements of group 8A; under normal conditions these elements exist as monoatomic gases.
(Note: monoatomic - consisting of one atom)

Question 29

Atomic Size (Radius)

Answer 29

The distance from its nucleus to the approximate outer boundary of its electron cloud.
From top to bottom: atomic size increases
From left to right: atomic size decreases

Question 30

Effective Nuclear Charge

Answer 30

The net force of nuclear attraction experienced by the valence electrons

Question 31

Ionization Energy (IE)

Answer 31

Ionization energy is defined as the minimum energy required to remove the most loosely held electron from an atom or an ion at its gaseous, ground state. To ionize an atom means to remove an electron from it.
From top to bottom: decrease in magnitude of the IE
From left to right: IE increases

Question 32

Electron Affinity (EA)

Answer 32

Electron affinity, EA, is defined as the energy change associated with the addition of an electron to an atom or an ion at is gaseous, ground state
From top to bottom: EA becomes more positive/less negative (Note: becomes less favourable to add an electron as the distance from the nucleus increases)
From left to right: EA becomes more negative/less positive (Note: becomes more favourable)

Question 33

Electronegativity

Answer 33

The measure of the ability of an atom to attract electrons in a bond. Electronegativity values are based on a variety of properties such as ionization energy and electron affinity.
Bottom left to top right: electronegativity increases (Note: with exception of Nobel gases, 8A)

Question 34

What is the most electronegative atom?

Answer 34

Fluorine

Question 35

What is the least electronegative atom?

Answer 35

Francium and cesium

Question 36

Covalent Bond (Non-Polar Covalent Bond)

Answer 36

When the electronegativity difference (ΔEN) between 2 atoms is zero or very small, a covalent bond is formed between them. This means that the electrons are shared equally by the 2 atoms.

Question 37

Polar Covalent Bond

Answer 37

If the ΔEN is intermediate, the bond is polar covalent, in which case the shared electrons spend more time around the more electronegative atom. The more electronegative atom pulls he shared electron cloud more towards itself.
(Note: since the electron density is greater around the more electronegative atom, it is said to have a partial negative charge (δ-), and the less electronegative has a partial positive charge (δ+).)

Question 38

Ionic Bond

Answer 38

In general, when the ΔEN between 2 atoms is large, an ionic bond is formed between them. In the formation of an ionic bond, one or more valence electrons are completely transferred from the less electronegative atom (metal) to the more electronegative atom non-metal) producing positive and negative ions. The electrostatic force of attraction between oppositely charged ions is what we call ionic bond.

Question 39

Cation

Answer 39

When an atom loses one or more electrons, a positive ion, or a cation is formed

Question 40

Anion

Answer 40

When an atom gains one or more electrons, a negative ion, or a anion is formed

Question 41

Atomic Mass

Answer 41

The atomic mass of an element is a weighted average of the masses of the isotopes of that element.

Question 42

Average Atomic Mass

Answer 42

The average atomic mass of an element is usually called the atomic mass of that element for simplicity

Question 43

Main Group Elements (Representative Elements)

Answer 43

Known as A block elements

Groups: 1,2,13-18

Question 44

Transition Metals

Answer 44

Known as B block elements

Groups: 3-12

Question 45

Inner Transition Metals (Rare Earth Metals)

Answer 45

Lanthanides and Actinides

Question 46

Periodic Trends: Why should the element be in the gaseous state?

Answer 46

When an element is in the gaseous state, the atoms are far apart from each other, and there is no force of attraction between them. This means that an electron in an atom is only attracted by the nucleus of that atom, and is not influenced by the nuclei of the surrounding atoms.

Question 47

Periodic Trends: Why should the element be in the ground state?

Answer 47

The ground state (or the relaxed state) or an atom is the state at which the electrons of the atom are where they should be. When they are given sufficient energy, they jump to higher energy levels; electrons are said to be in “excited” states. We want all atoms to be at there ground states when we begin to use energy to ionize them so that we can have the same reference point for comparison purposes.

Question 48

What is a chemical bond?

Answer 48

A chemical bond is a strong attractive force between 2 atoms in a molecule of between 2 ions. We can predict the type of bond that can be formed between 2 atoms based on their affinities for electrons.