Ions

Ions

Stable Atoms • A stable atom contains 8 valence electrons (or 2 for helium) • Atoms that do not contain 8 valence electrons in the neutral state tend to gain, lose, or share electrons. – Atoms in the neutral state have equal numbers of protons and electrons

What changes during a reaction? • Only electrons are involved in chemical reactions • In chemical reactions, the number of protons and the number of neutrons remains constant

Which elements gain or lose electrons? • • • • •

Group 1 – loses 1 electron Group 2 – loses 2 electrons Group 16 – gains 2 electrons Group 17 – gains 1 electron Group 18 – is stable so it does not gain or lose

Which elements gain or lose electrons? • The elements in groups 13-15 are less likely to gain or lose electrons because they have 3, 4, and 5 valence electrons. • Most of the transition elements tend to lose electrons

Practice • How many electrons does F- have?

Practice • How many electrons does F- have?  F is atomic number 9  F has 9 protons  A neutral F has 9 electrons

 F- has an additional unit of negative charge so it has one more electron

 F- has 10 electrons

More Practice • How many valence electrons does Clhave?

More Practice • How many valence electrons does Clhave?  Cl has 17 protons (atomic number 17)  Cl has 7 valence electrons when neutral  Cl- has one extra negative electron  Cl- has 8 valence electrons

More Practice • How many valence electrons does Mg2+?

More Practice • How many valence electrons does Mg2+?  Mg has 2 valence electrons  Mg2+ has 2 less electrons that result in a positive charge of 2 units.  REMEMBER: # of protons does not change!  Mg2+ has 8 valence electrons  This is because you go back to the previous energy level

More Practice • How many valence electrons does O2have? • How many valence electrons does Li+ have? • How many valence electrons does Na+ have? • How many valence electrons does Brhave?