Subscribe

9th grade · Science · Unit 4 of 10

Electrons & Compounds

Why atoms bond and what they make

What your child practices

How valence electrons decide whether atoms gain, lose or share electrons, ionic and covalent compounds, and reading simple chemical formulas.

Alaska content standards learning standard: HS-PS1-1; HS-PS1-2 · how outer electrons explain bonding and chemical reactions

How we explain it

Children can open this short lesson before they practice.

  1. Atoms gain, lose or share electrons to get a full outer shell.
  2. Metals lose electrons and non-metals gain them to form ionic compounds, like sodium chloride.
  3. Non-metals share electrons to form covalent compounds, like water (H₂O).

Example: Which pair most likely forms an ionic compound: carbon and oxygen, or potassium and chlorine? Ionic compounds form between a metal and a non-metal. Potassium is a metal; chlorine is a non-metal. Answer: potassium and chlorine

Electrons & Compounds in Alaska

In the Alaska content standards, this is unit 4 of 10 in 9th grade Science, after Atoms & Electrons and before Photosynthesis & Respiration.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alaska Department of Education and Early Development

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Which pair would most likely form a covalent compound?

    • calcium and oxygen
    • potassium and bromine
    • sodium and chlorine
    • carbon and oxygen

  2. Question 2

    Which type of bond forms when atoms share electrons?

    • ionic
    • covalent
    • nuclear
    • magnetic

  3. Question 3

    What charge does an ion of a Group 2 element (like calcium) usually have?

    • +2
    • 0
    • −2
    • +1

  4. Question 4

    Ionic compounds usually have high melting points because…

    • they are always gases
    • the attraction between ions is strong
    • they have no bonds
    • they are very light

  5. Question 5

    What does the formula CO₂ tell you?

    • Carbon dioxide is an element
    • Carbon is an oxygen ion
    • One carbon atom and two oxygen atoms are in each molecule.
    • Two carbon atoms and one oxygen atom

  6. Question 6

    Why does chlorine (7 valence electrons) form a negative ion?

    • It loses seven electrons.
    • It loses a proton.
    • It never bonds.
    • It gains one electron to fill its outer shell.

More 9th grade