Warmup What is the name and symbol of this atom? What is it’s atomic #? Mass #? Atomic mass? Can you draw the electron rings around it? 19 protons 20 neutrons

Ionic: very strong, creates solids. 3 types of bonds Ionic: very strong, creates solids. Polar: medium strength bond. Some solids, liquids, and gases Covalent: very weak bond. Some solids, liquids, gases

Bond type depends on how electrons are shared between atoms Electronegativity: An atom’s attraction for electrons High EN = strong attraction Low EN = low attraction

How to figure out bond type: You must calculate at the electronegativity difference between the two atoms Use the approximate guideline for electronegativity differences: 0.0 – < 0.5 = covalent (electrons shared nicely) 0.5 – < 2.0 = polar covalent (electrons being pulled from stronger atom) 2.0 – 4.0 = ionic (electrons stolen/transferred by stronger atom

Use these values provided to help:

Examples: H and Cl 2.1 – 3.0 Difference = 0.9 = polar C and H 2.5 – 2.1 Difference = 0.4 = covalent

Examples: Na and Cl 0.9 – 3.0 Difference = 2.1 = ionic Also notice that you have a metal bonded to a nonmetal! Follow this link for a video recap: https://www.youtube.com/watch?v=02Q352- Y7iU

Atoms: # protons = # electrons Ions: # protons ‡ # electrons Atoms vs. ions Atoms: # protons = # electrons Atoms are neutral (no charge) Ions: # protons ‡ # electrons Electron has been ripped off by stronger EN atom Ions have either a positive or negative charge. Ions are atoms that have gained or lost electrons.

WhY do atoms gain/lose electrons? All atoms want to look like a noble gas. Noble gases are “inert” = non-reactive Why don’t they react? They have full valence electron shells. All noble gases (except He) have 8 valence electrons! So all other atoms will either gain or lose electrons to have 8 valence electrons, too!

Cations: atoms that have LOST electrons and have a POSITIVE charge. Two types of ions Cations: atoms that have LOST electrons and have a POSITIVE charge. Anions: atoms that have GAINED electrons and have a NEGATIVE charge.

Has 11 protons and 11 electrons. Draw the electrons in: Example #1: sodium Sodium: atomic #11 Has 11 protons and 11 electrons. Draw the electrons in: 11 p+ Remember: 1st ring: 2 electrons max 2nd ring: 8 electrons max 3rd ring: 18 electrons max

Example #1: sodium Notice that this atom has 1 valance electron. Sodium has 2 choices: lose 1 electron to look like Neon Or gain 7 more electrons to be like Argon. Atoms are lazy…they take the easiest option! Sodium will LOSE 1 ELECTRON! 11 p+

What does sodium look like now? Still has 11 protons Example #1: sodium What does sodium look like now? Still has 11 protons Now has only 10 electron Protons are positive Electrons are negative (+11)+(-10) = +1 charge 11 p+

Has 17 protons and 17 electrons. Draw the electrons in: Example #2: Chlorine Chlorine: atomic #17 Has 17 protons and 17 electrons. Draw the electrons in: 17 p+ Remember: 1st ring: 2 electrons max 2nd ring: 8 electrons max 3rd ring: 18 electrons max

What does chlorine want to do? Chlorine has 2 choices: Lose all 7 valence electron Gain 1 more valence electron Much easier to just gain 1 17 p+

What does chlorine Look like now? Still has 17 protons Now has 18 electrons (+17)+(-18) = -1 charge 17 p+

What happens when sodium and chlorine “find” each other? Notice sodium has 1 extra electron to give away and chorine WANTS one electron? 11 p+ 17 p+ sodium chlorine

Ionic bonding One atom must lose electrons (it’s always the metals on the periodic table) Caton (positive) One atom must gain electrons (it’s always the nonmetals on the periodic table) Anion (negative) Metal + nonmetal = ionic bond Positive + negative attract!