Transcript Ions
Ions Chemistry 1 What are they? Ions are charged atoms (or groups of atoms) Have either gained or lost electrons Characteristics of Ions •Conduct electricity •Like charges repel •Opposite charges attract Electrical Conductivity e- e- e- e- e- e- e- e- e- e- e- e- e- Metals conduct electricity because the electrons are held loosely by each atom. When an electron is added to one end, another electron will be bumped off the opposite end. e- Electrical Conductivity Ionic compounds can conduct electricity ONLY when the ions are free to move about. (i.e. They must be either melted or dissolved.) Ionic compound Dissolved in water Why are they charged? •Atoms have both p+ and e-. If these are present in equal numbers the +/- charges will balance out. •If they are in unequal numbers the result is an ion Na+ e.g. Na 11e- 11p+ 11p+ 10e+ 1 e- Why are they charged? e.g. Mg Mg2+ 12e12p+ 10e12p+ + 2 e- Why are they charged? e.g. F F10e- 9e9p+ + 1 e- 9p+ One word of Caution: Keep your hands off the nucleus!! You don’t know where it’s been. You are NOT allowed to move protons, only electrons Nomenclature Cation: a positive ion Has lost 1 or more eC, a + ion. (the cat’s eyes are + signs) Anion: a negative ion Has gained 1 or more eA Negative Ion Insert your own cute picture here Nomenclature - cations Cations: Metals – lost electron(s) Name is the same as the name of the atom. e.g. K+ = potassium (ion) K = potassium Na = sodium Na+ = sodium (ion) Mg = magnesium Mg2+ = magnesium (ion) Ca = calcium Ca2+ = calcium (ion) Nomenclature - anions Anions: Non-metals – gained electron(s) Name is the same as the name of the atom w/ the ending changed to “-ide”. e.g. Cl = chlorine Cl- = chloride F = fluorine F- = fluoride N = nitrogen N3- = nitride O = oxygen O2- = oxide Predicting Charges •Noble gases are inherently stable. •Electrons are responsible for chemical reactivity. •Might guess that the number of electrons on Noble gases must be very stable. Assume that atoms will either gain or lose electrons to end up with the same number of electrons as the nearest Noble gas Predicting Charges - huh? Find the element on the periodic table - what is its atomic number? Find the nearest Noble gas (Nobel gases are the elements in the far right column. The nearest will have an atomic number closest to the element you’re trying to predict) Calculate how many electrons must be added or removed. Predicting Charges - practice Predict the charge on an ion formed by Iodine (I) What’s Iodine’s atomic number? 53 What’s the nearest Noble gas? Xenon (Xe) Does I need to gain or lose e- to have the same number of e-’s as Xenon? How many? Gain 1 electron So what’s the charge? 1- (or -1 is okay) Predicting Charges - practice Predict the charge on an ion formed by Bromine (Br) What’s bromine’s atomic number? 35 What’s the nearest Noble gas? Krypton (Kr) Does Br need to gain or lose e- to have the same number of e-’s as Krypton? How many? Gain 1 electron So what’s the charge? 1- (or -1 is okay) Predicting Charges - practice Predict the charge on an ion formed by Sulfur (S) What’s sulfur’s atomic number? 16 What’s the nearest Noble gas? Argon (Ar) Does S need to gain or lose e-’s to have the same number of e-’s as Argon? How many? Gain 2 electrons So what’s the charge? 2- (or -2 is okay) Predicting Charges - practice Predict the charge on an ion formed by Potassium (K) What’s potassium’s atomic number? 19 What’s the nearest Noble gas? Argon (Ar) Does K need to gain or lose e-’s to have the same number of e-’s as Argon? How many? Lose 1 electron So what’s the charge? 1+ (or +1 is okay)