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NES 205 · COURSE

NES 205 Middle Grades General Science course

26 guided lessons across 3 sections. Read the first chapter free — no account needed.

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Atoms and the Periodic Table

A periodic table is a map of what atoms can do.

Key words

Atoms
An atom has protons and neutrons in a nucleus, with electrons around it. — e.g. An oxygen atom has eight protons.
Identity
Proton number determines the element; changing neutrons makes an isotope. — e.g. Carbon-12 and carbon-14 are both carbon.
Ions
Losing electrons makes a positive ion; gaining electrons makes a negative ion. — e.g. Sodium loses one electron to form Na+.
Periods
Rows track occupied electron shells; columns often share valence patterns. — e.g. Lithium and sodium both form +1 ions.
Trends
Metals tend to lose electrons; nonmetals tend to gain or share them. — e.g. Magnesium commonly forms Mg2+.

I DO — ATOMS

An atom has protons and neutrons in a nucleus, with electrons around it. Example: An oxygen atom has eight protons. Important distinction: An atom is not a tiny solid ball.

IDENTITY

Proton number determines the element; changing neutrons makes an isotope. Example: Carbon-12 and carbon-14 are both carbon. Important distinction: Changing neutrons does not create another element.

WE DO — IONS

Losing electrons makes a positive ion; gaining electrons makes a negative ion. Example: Sodium loses one electron to form Na+. Important distinction: An ion does not form by changing protons.

PERIODS

Rows track occupied electron shells; columns often share valence patterns. Example: Lithium and sodium both form +1 ions. Important distinction: Same row does not mean same chemical behavior.

YOU DO — TRENDS

Metals tend to lose electrons; nonmetals tend to gain or share them. Example: Magnesium commonly forms Mg2+. Important distinction: All elements are not equally reactive.

Remember this

  • ATOMS: An atom has protons and neutrons in a nucleus, with electrons around it.
  • IONS: Losing electrons makes a positive ion; gaining electrons makes a negative ion.
  • TRENDS: Metals tend to lose electrons; nonmetals tend to gain or share them.

Remember ATOMS, IDENTITY, IONS: ATOMS = an atom has protons and neutrons in a nucleus, with electrons around it / IDENTITY = proton number determines the element; changing neutrons makes an isotope / IONS = losing electrons makes a positive ion; gaining electrons makes a negative ion.

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Every lesson in the course

I. Physical Science

40%
  1. Atoms and the Periodic TableFree
  2. Bonds, Compounds, and Mixtures
  3. Density, Solutions, and Nuclear Matter
  4. Physical and Chemical Change
  5. Moles, Reactions, and Rates
  6. Gases and Phase Changes
  7. Energy Transfer and Thermodynamics
  8. Circuits and Magnetism
  9. Waves, Light, and Sound
  10. Forces, Motion, and Engineering

II. Life Science

30%
  1. Cell Types and Organelles
  2. Membranes, Homeostasis, and Systems
  3. Photosynthesis and Cellular Respiration
  4. Cell Division and Life Cycles
  5. DNA, Genes, and Inheritance
  6. Evolution, Classification, and Evidence
  7. Ecosystems, Energy, and Matter
  8. Populations, Biomes, and Human Impacts

III. Earth and Space Science

30%
  1. Solar System, Gravity, and Orbits
  2. Stars, Galaxies, and Universe
  3. Earth Layers and Plate Tectonics
  4. Rocks, Minerals, and Geologic Time
  5. Weathering, Erosion, and Resources
  6. Water Cycle and Freshwater
  7. Atmosphere, Weather, and Climate
  8. Oceans, Hazards, and Sustainability
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