Atoms & Ions

Atoms: Building blocks of life, has central nucleus (protons & neurons)

Elements: Substance made out of one single atom (noble gases and non-metals)

Compounds: Made of different types of atoms/ions, chemically bonded in fixed ratios

Mixtures: Different substances in the same physical space but not chemically combined, allowing each substance to retain its own properties. Can be physically seperated

Molecules: Substance made of 2 or more non-metal atoms

Central nucleus: Protons with +1 charge (positive) and electrons with -1 charge (negative). Positive and negative are attracted, that’s why electrons don’t fly away, held by nucleus.

Protons have mass of 1 same as neutron. Electron have 1/1836 of protons

Chemical symbols

Atomic number: No. of protons (that means same as number of electrons for neutral atom) this is the number on the periodic table

Mass number: No. of protons and neutrons (always the largest number in chemical symbol)

Group: Vertical column shows how many valence electrons an element has

Period: Row that shows number of occupied electron shells

• Ground state: Lowest energy arrangement (e.g., 2, 8, 1)

• Excited state: One or more electrons jump to a higher shell (e.g., 2, 7, 2 for sodium if excited)

Ions form when atoms gain or lose electrons to achieve a full valence shell

• Metals lose electrons → form cations (+)

• Non-metals gain electrons → form anions (−)

/✅ I can predict charges on monatomic ions using the periodic table:

• Group 1 → +1

• Group 2 → +2

• Group 13 → +3

• Group 15 → −3

• Group 16 → −2

• Group 17 → −1

• Group 18 → 0 (stable)

Ionic Compounds

Formed when metals and non-metals join together to form ionic bond. Opposite attract = cation + anion