Science test

Summary Sheet For Science Test

Periodic Table Trends – Test Notes

πŸ”Ή Periodic Table Basics:

  • Organized by atomic number (protons).

  • 18 groups (columns ↓), 7 periods (rows β†’).

  • Group (↓) = column (same valence electrons).

  • Period (β†’) = row (same number of electron shells).

πŸ”Ή Group Trends (↓):
βœ… Atomic mass increases down a group.
βœ… Number of electron shells increases down a group.
βœ… Same number of valence electrons in a group.

πŸ”Ή Period Trends (β†’):
βœ… Atomic mass generally increases left to right.
βœ… Valence electrons increase left to right.
βœ… Same number of electron shells (equal to period number).

πŸ“Œ Remember: Period number = Number of electron shells!



Classification of Matter – Test Notes

πŸ”Ή Matter β†’ Anything that takes up space and has mass.

1. Pure Substances

βœ… Contain only one kind of particle (atom or molecule).
βœ… Cannot be separated by physical means.
βœ… Examples: Gold, sugar, pure water.

πŸ”Έ Elements

  • Cannot be broken down into simpler substances.

  • Made of a single type of atom (found on the periodic table).

  • Examples: Gold (Au), Zinc (Zn), Copper (Cu), Iron (Fe).

πŸ”Ή Metals (Left & Center of Periodic Table)

  • Examples: Gold, Zinc, Copper, Iron.

πŸ”Ή Non-Metals (Right Side of Periodic Table)

  • Examples: Oxygen (O), Nitrogen (N), Helium (He).

πŸ”Έ Compounds

  • Contain two or more different elements in a fixed proportion.

  • Examples: Sugar, Water (Hβ‚‚O), Salt, Baking Soda, COβ‚‚.



2. Mixtures

βœ… Contain two or more pure substances.
βœ… Can be separated by physical means.
βœ… Examples: Alloy, sea water, tea, tap water, granola bar.

πŸ”Έ Homogeneous Solutions

  • Uniform mixture (cannot see different parts).

  • Examples: Sea water, alloys, tap water, tea.

πŸ”Έ Heterogeneous Mixtures (Mechanical Mixtures)

  • Different parts can be clearly seen.

  • Examples: Granola bar, lemonade (with pulp), salad.



πŸ“ Key Differences:

  • Pure Substances = One kind of particle.

  • Elements = One type of atom.

  • Compounds = Two or more different elements.

  • Mixtures = Two or more pure substances.

    • Homogeneous = Looks the same throughout.

    • Heterogeneous = Different parts visible.



How to Count Atoms – Test Notes

πŸ”Ή Chemical Symbol β†’ Represents one atom of an element.

  • Example: Na = 1 sodium atom.

πŸ”Ή Subscript β†’ Small number at the lower right of an element symbol.

  • Indicates the number of atoms of that element.

  • Example: Hβ‚‚ = 2 hydrogen atoms.

πŸ”Ή Coefficient β†’ Large number in front of a chemical formula.

  • Multiplies the number of atoms of each element in the formula.

  • Example:

    • 2Hβ‚‚O β†’ 4 hydrogen atoms, 2 oxygen atoms.

    • 3CuSOβ‚„ β†’ 3 copper (Cu), 3 sulfur (S), 12 oxygen (O).

    • 4Pb(NO₃)β‚‚ β†’

      • 4 lead (Pb),

      • (NO₃)β‚‚ means 2 nitrogen (N) & 6 oxygen (O) per molecule

      • Multiply by 4: 8 nitrogen (N), 24 oxygen (O).

βœ… REMEMBER:

  • Subscript applies only to the element before it.

  • Parentheses ( ) β†’ Apply the subscript to everything inside.

  • Coefficient multiplies everything in the formula.



Inside the Atom – Test Notes

Types of Subatomic Particles

Atoms are made of 3 subatomic particles:

1⃣ Proton (p⁺) β†’ Positive charge (+1)

  • Mass: 1 atomic mass unit (amu)

  • Location: Inside nucleus

2⃣ Neutron (n⁰) β†’ Neutral (no charge)

  • Mass: 1 atomic mass unit (amu)

  • Location: Inside nucleus

3⃣ Electron (e⁻) β†’ Negative charge (-1)

  • Mass: ~1/1836 of a proton (very small)

  • Location: Electron shells orbiting the nucleus

βœ… Atoms are electrically neutral, meaning:

# of Protons = # of Electrons

Atomic Number

πŸ”Ή The atomic number = number of protons in an atom.
πŸ”Ή Determines the element's identity on the periodic table.
πŸ”Ή In a neutral atom, the # of protons = # of electrons.

βœ… REMEMBER:

  • Atomic number = # of protons = # of electrons (if neutral)

  • Mass number = Protons + Neutrons

  • Neutrons = Mass number - Atomic number