C5.1 - Atoms

Physical Properties of Alkali Metals

Atomic size increases as you go down the group, melting point decreases, and density increases.

Conductivity of Alkali Metals

Good conductors of electricity.

Softness of Alkali Metals

Soft and can be cut with a knife.

Appearance of Alkali Metals when cut

Silvery when freshly cut.

Density of Alkali Metals

Low density; some can float on water.

Reactivity of Alkali Metals

Reactivity increases as you go down the group.

Electron Loss in Alkali Metals

Lose 1 electron easily, creating more shields and a large atomic radius.

Lithium + Water yields

Hydrogen + Lithium Hydroxide

Sodium + Water yields

Hydrogen + Sodium Hydroxide

Uses of Lithium

Used in batteries (especially rechargeable ones in electric cars) and as a mood stabilizer in medicine.

Uses of Sodium

Used in titanium production, as a coolant in nuclear reactors, and helps move nutrients/waste in the body.

Uses of Potassium

Helps the heart to function well.

Mitosis

The process of cell division resulting in two genetically identical daughter cells.

Growth Phase (1)

The first stage of the cell cycle where the number of sub-cellular structures like mitochondria and ribosomes doubles.

Growth Phase (2)

Part of the Growth Phase where DNA replicates to form two copies of each chromosome

Growth Phase (3)

Part of the Growth Phase which includes growth and the DNA being checked for mistakes and any corrections made.

Mitosis

Cell division

Mitosis

DNA lines up on the equator (middle of the cell)

Mitosis

Chromosome separates and is pulled to the poles of the cell

Nucleus

Separates

Daughter cells

Two genetically identical cells are made.

Halogens

Non-metals that do not conduct electricity, are brittle and crumbly when solid, and are poisonous and smelly.

Atomic radius of Halogens

Increases as you go down the group.

Melting and Boiling Points of Halogens

Increase as you go down the group.

Reactivity of Halogens

Decreases down the group as it's harder to gain an electron (larger atoms, more shielding).

Displacement Reaction Example

Chlorine displaces Bromine from KI: Cl2 + 2KBr -> 2KCl + Br2

Chlorine Uses

Bleaching agent, water purification, pesticides

Fluorine Uses

Dental care, toothpaste, flouridation

Bromine Uses

Flame retardants, antiseptic

Iodine Uses

Thyroid function, photographic materials

Mendeleev

Russian scientist who arranged the periodic table based on relative atomic masses in 1869.

Mendeleev's Periodic Table Design

Mendeleev designed his table using known elements and arranged them by properties.

Mendeleev's Gaps

Mendeleev left gaps for undiscovered elements in his periodic table.

Elements Predicted by Mendeleev

Atomic weight, state at room temperature, melting/boiling points, metallic or non-metallic properties.

Modern Periodic Table Arrangement

Elements arranged by atomic number.

Group Numbers on Periodic Table

Indicates the number of electron shells.

Periods on Periodic Table

Indicates the number of electron shells.

John Newlands

English scientist who suggested the Law of Octaves in 1864.

Law of Octaves

Each element is similar to the element eight places further on.

Johann Doberiener

German scientist who suggested the Law of Triads in 1817.

Law of Triads

Important if you calculate the average atomic mass.

Helium

Element symbol: He; Discovered: N/A; Origin of the Name: From Greek word 'Helios' meaning 'sun'; Atomic Number: 2; State at 20°C: Gas; Melting Point: -272.2°C; Uses: Balloons, airships, super-magnets

Neon

Element symbol: Ne; Discovered: 1898; Origin of the Name: From Greek word meaning 'New'; Atomic Number: 10; State at 20°C: Gas; Melting Point: -243.6°C; Uses: Neon signs, high voltage indicators.

Argon

Element symbol: Ar; Discovered: 1894; Origin of the Name: From Greek word 'Argos' meaning 'inactive'; Atomic Number: 18; State at 20°C: Gas; Melting Point: -189.4°C; Uses: Shielding in welding, lighting in high intensity bulbs.

Krypton

Element symbol: Kr; Discovered: 1898; Origin of the Name: From Greek word meaning 'hidden'; Atomic Number: 36; State at 20°C: Gas; Melting Point: -157.4°C; Uses: Photographs, high productive vacuum tubes.

Xenon

Element symbol: Xe; Discovered: 1898; Origin of the Name: From Greek word meaning 'strange'; Atomic Number: 54; State at 20°C: Gas; Melting Point: -111.8°C; Uses: Lighting in high intensity bulbs

Respiration

Releasing energy from glucose in all living cells.

Mitochondria

The location where aerobic respiration takes place.

Aerobic Respiration

Respiration with oxygen, occurring in the mitochondria, where glucose is completely broken down.

Aerobic Respiration Equation

Glucose + Oxygen -> Carbon Dioxide + Water (C6H12O6 + 6O2 -> 6H2O + 6CO2)

Exothermic Reaction

An exothermic reaction that gives out energy.

Anaerobic Respiration

Respiration without oxygen, occurring in the cytoplasm.

Anaerobic Respiration (Plant)

Glucose -> Ethanol + Carbon Dioxide (used in bread/alcohol making)

Anaerobic Respiration (Animal)

Glucose -> Lactic Acid

Oxygen Debt (Lactic Acid)

Builds up during anaerobic respiration in animals and is repaid with oxygen.

Lactic Acid Recovery

Lactic Acid + Oxygen -> Carbon Dioxide + Water

Photosynthesis

Plant cells, chloroplasts absorb sunlight.

Endothermic Reaction

An endothermic reaction that takes in energy.

Photosynthesis Equation

Water + Carbon Dioxide -> Glucose + Oxygen (6H2O + 6CO2 -> C6H12O6 + 6O2)

John Dalton

Born in 1903, Summarized atomic theory: All elements are made of atoms; atoms of the same element are identical; atoms cannot be created, destroyed, or split.

Solid Sphere Model

Atomic model proposed by John Dalton where atoms are solid and indivisible spheres.

Neils Bohr

Born in 1913, created the Bohr model, and was a theoretical physicist.

Planetary Model

Atomic model proposed by Neils Bohr, depicting electrons orbiting the nucleus in fixed paths.

Joseph John Thompson

Discovered electrons in 1897 and proposed the Plum Pudding Model.

Plum Pudding Model

Atomic model proposed by J.J. Thompson, depicting atoms as balls of positive matter with negative electrons embedded within.

Ernest Rutherford

Discovered protons in 1911 and proposed the nuclear model of the atom.

Gold Foil Experiment

Experiment conducted by Rutherford that led to the conclusion that atoms are mostly space with a small, positive nucleus.

Nuclear Model

Atomic model with a small, dense, positively charged nucleus surrounded by mostly empty space.

Atom Radius

Radius of an atom is about 0.1 nm on average.

Neutral Atom

Atoms are neutrally charged when the number of neutrons and protons are the same.

Proton

Positive charge, same mass as a neutron.

Electron

Nearly nothing in mass, negative charge.

Neutron

Neutral charge, some mass as proton.

Atomic Number

Number of protons equals the number of electrons.

Mass Number

Number of protons plus number of neutrons.

Group Number (Periodic Table)

Shows how many outer shells it has.

Period Number (Periodic Table)

Shows how many electron shells there are.

Isotope

An element with the same number of protons but a different number of neutrons. They have the same atomic number but different mass numbers.

Unstable Isotopes

Some isotopes are unstable and as a result decay and give off radiation.

Ar (Relative Atomic Mass)

% of Isotope A x mass of isotope A / 100 + % of Isotope B x mass of isotope B / 100