Calculate Relative Atomic Mass

Relative Atomic Mass

• Calculated by: (abundance percentage x atomic mass) + (abundance percentage x atomic mass) / 100
• Used to determine the average mass of an element

Characteristics of Atoms

• Chemical nature depends on the number of electrons
• Isotopes have the same chemical properties but different physical properties due to varying numbers of neutrons

Periodic Table Group Properties

Group 1 - Alkali Metals

• Valence: 1
• Highly reactive, easily lose their outer electron to obtain a complete outer shell
• Not readily found in nature
• Reactivity increases as you move down the group (ionization energy decreases)
• Good conductors of heat and electricity
• Soft and malleable

Group 2 - Alkaline Earth Metals

• Valence: 2
• Highly reactive, easily lose their outer electron to obtain a complete outer shell
• Not readily found in nature
• Reactivity increases as you move down the group (ionization energy decreases)
• Good conductors of heat and electricity
• Shiny

Group 7 - Halogens

• Valence: 7
• May be solid, liquid, or gas
• Highly reactive, strong electronegativity (tends to 'steal' electrons from other elements)

Group 8 - Noble Gases

• Maximum number of electrons in outer shell
• Extremely high ionization energy
• Unreactive

Transitional Metals

• Can have multiple valencies (e.g. Fe: Fe2+, 3+)
• Good conductors of heat and electricity
• Malleable and ductile

Lanthanides and Actinides

• Have 2 electrons in outer shell
• Good electrical conductors
• Silver: tarnishes easily

Radioactive Elements

• Have more than 82 protons
• Unstable nuclei due to proton-to-neutron ratio
• Release radiation and may have short or long half-lives

Atomic Radius

• Increases down a group due to additional energy levels and electrons
• Decreases from left to right across a period due to electrostatic attractions

Ionic Charge and Radius

• Atoms tend to lose or gain electrons to achieve complete s and p sublevels

Bonding

Metallic Bonding

• Involves the electrostatic attraction between metal ions that have released electrons
• Valence electrons are loosely held as metal (low ionization energy)
• Forms positively charged cations
• Delocalized electrons are free to move randomly
• Overall neutral charge (number of cations = number of delocalized electrons)
• Non-directional

Learn how to calculate the relative atomic mass of an element using the formula provided in the image. Understand how the abundance percentage and atomic mass of isotopes contribute to determining the relative atomic mass.