Week 2: Cell chemistry: atoms and their ions 2.1 Arranging electrons in atoms [4.6] 2.2 Valence electrons [4.7] 2.3 Electron dot structures [4.7] 2.4 The formation of ions [6.1] 2.5 Cations and anions [6.1] Readings: Chemistry Textbook. Timberlake (2015). Chemistry (12th edn.). Pearson Australia. LFS103 Vol. 2 Custom textbook Ch 4: Concepts 4.6, 4.7 Ch 6: Concept 6.1

Week 2: Learning objectives Describe for the first 20 elements of the periodic table; the Z value, the valance electrons, the electron configuration and the electron dot structures. Explain if an element is stable or reactive using its electron configuration. Understand how an ion is formed. Use the octet rule to write the symbols of the simple ions for the first 20 elements. Explain which elements form cations and which elements form anions, and why.

Metals Lose Their Valence Electrons to Form Positive Ions (Cations) 2.5 Cations and anions [6.1] Metals Lose Their Valence Electrons to Form Positive Ions (Cations) The metal sodium (Z = 11) Shell 3 Na 2e- 8e- 1e- Sodium atom with 1 valence electron

Metals Lose Their Valence Electrons to Form Positive Ions (Cations) 2.5 Cations and anions [6.1] Metals Lose Their Valence Electrons to Form Positive Ions (Cations) The metal sodium (Z = 11) Shell 3 + Loss of one valence electron Na Na 2e- 8e- 1e- 2e- 8e- Sodium atom with 1 valence electron Sodium ion with a stable electron configuration.

2.5 Cations and anions [6.1] Figure from page 167, Timberlake (2015)

Metals Lose Their Valence Electrons to Form Positive Ions (Cations) 2.5 Cations and anions [6.1] Metals Lose Their Valence Electrons to Form Positive Ions (Cations) The metal magnesium (Z = 12) Shell 3 2+ Loss of two valence electrons Mg Mg 2e- 8e- 2e- 2e- 8e- Magnesium atom with 2 valence electron Magnesium ion with a stable electron configuration.

2.5 Cations and anions [6.1] Figure from page 168, Timberlake (2015)

Metals form Cations Metals Ionic Charge Examples 2.5 Cations and anions [6.1] Metals form Cations Metals Ionic Charge Examples Group 1A: Form 1+ ions Li+, Na+, K+ Group 2A: Form 2+ ions Mg2+, Ca2+ Group 3A: Form 3+ ions Al3+

What ion does Beryllium form?

2.5 Cations and anions [6.1] Non-Metals Gain Electrons to Form Negative Ions (Anions) and Fill Their Outer Shell The non-metal chlorine (Z = 17) Shell 3 _ Gain one valence electron Cl 2e- 8e- 7e- Cl 2e- 8e- 8e- Chlorine atom with 7 valence electrons Chlorine ion with a stable electron configuration.

2.5 Cations and anions [6.1] Figure from page 168, Timberlake (2015)

Non-Metals form Anions 2.5 Cations and anions [6.1] Non-Metals form Anions Non-Metals Ionic Charge Examples Group 4A: Do not form ions very often Group 5A: Form 3- ions N3-, P3- Group 6A: Form 2- ions O2-, S2- Group 7A: Form 1- ions F-, Cl- Group 8A: Noble gases - do not form ions

What ion does Sulphur form?

Thinking Cations and Anions When an atom loses its valence electrons, it has less negative (-) electrons than positive (+) protons. It becomes a cation. + Atom Cation Lose one e- 2+ Atom Cation Lose two e-

Thinking Cations and Anions When an atom gains electrons, it has more negative (-) electrons than positive (+) protons. It becomes an anion. - Atom Anion Gain one e- 2- Atom Anion Gain two e-

Summary of common cations and anions to reach Noble Gas state.