AS Level Chemistry - Summer Study

Element

A substance with the same number of protons.

Compound

2 or more elements that are Chemically combined. Thus, they cannot be physically separated.

Mixture

A substance that is physically combined. Can be separated via filtering, evaporation, etc.

What is the mass and charge of an Electron?

Mass: 1/1840 (Negligible)
Charge: -1

What is the mass and charge of a Proton?

Mass: 1
Charge: +1

What is the mass and charge of a Neutron?

Mass: 1
Charge: 0

What is Relative Atomic Mass?

1/12th the mass of Carbon-12. It has no units.
It is used to express the average mass of elements.

Valence Shell

The outermost Electron shell/ Orbital/ Energy Level

Farther away shells = more energy
More filled the shell = more stable

Noble Gases

• Elements in Group 8/0

• Have a full Valence Shell

• Unreactive and Stable

Isotopes

• Atoms with the same # of Protons

• But, different # of Neutrons

• Same chemical properties

• But, different physical properties (due to variety in Mass)

• Identical in Appearance

Formula for Calculating Relative Atomic Mass?

Ar = (% of Isotope A mass of Isotope A) + (% of Isotope B mass of Isotope B)…
100

What does Z, A, and X stand for in AZX notation?

X = Chemical Symbol of Element

Z = Number of Protons

A = Total Mass (Z + N or # of Neutrons)

Metals

Electron Arrangement: 1-3 Valence Electrons (more in groups 5, 6)
Conductivity: Good
Bonding: Metallic
Oxide: Basic Oxide
Reaction w/ Acid: Many react w/ acids
Physical Properties: Malleable, High Melting & Boiling Point

Non-Metal

Electron Arrangement: 4-7 valence electrons
Conductivity: Poor
Bonding: Covalent
Oxide: Acidic Oxide
Reaction w/ Acid: Doesn’t react
Physical Properties: Brittle, low boiling & melting point

What does the group # show?

Shows how many electrons and charge a METAL will lose and gain.
Shows how many electrons NON-METALS will need to gain to go back to a full outer shell. (if 6, it needs 2 more).
Same group = same valence electrons = similar characteristics.

Metalloids

Characteristics between metals and non-metals. On the right side as METALLIC CHARACTER decreases as you go right on the Periodic Table.

Alkaline Metals

• Group 1

• Properties:
  - Easy to cut
  - Shiny after being cut
  - Conducts heat/electricity
  - Low melting point
  - Low density

• Trends:
  - More reactive as period increases
  - Softer and Denser as period increases EXCEPT for SODIUM and POTASSIUM

What happens when Alkaline Metals react with Water?

• produces Alkaline Metalhydroxide Solution + Hydrogen Gas

• so, Alkaline Metals are usually kept in Oil

Halogens

• Group 7

• Properties:
  - Diatomic

  - Forms Halide Ions (as they try to gain 1 electron to fill the outer shell)

  - Poisonous

• Trends:
  - Density increases as you go DOWN
  - Reactivity decreases as you go DOWN
  - Boiling Point increases as you go DOWN
  - Color gets darker as you go DOWN

Why do Halogens reactivity decrease as you go down?

The elements at the top have less electrons →
outer electrons are closer to nucleus →
stronger electrostatic force between electrons and nuclei →
attracts extra electrons →
more reactive

What colors do the Halogens display?

Fluorine: Yellow
Chlorine: Yellow-Green
Bromine: Red-Brown
Iodine: Grey-Black (Solid), Purple (Gas) and Brown (Liquid)