Ions Valence Electrons

Review…with a partner Ions Cation Anion Ionization energy Electronegativity

Valence Electrons Electrons in the highest occupied energy level The number of valence electrons determines the chemical properties of an element To find the number of valence electrons of a representative element, look at its group number Group 1A has 1 valence electron Group 2A has 2 valence electrons Group 8A has 8 valence electrons (He is an exception)

Electron Dot structures Lewis structures Diagrams that show valence electrons as dots Don’t double up until you have a dot in each quadrant (He exception) All of the elements within a group (except He) have the same number of electron dots in their structure

Your Turn Fill in the following table with the correct Lewis structures Group Period 1A 2A 3A 4A 5A 6A 7A 8A 1 2 3 4

Octet Rule In forming compounds, atoms want the electron configuration of a noble gas. Octet=8 Noble gases(except He) ns2np6 and have 8 electrons in their highest occupied energy level Atoms of metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetals tend to gain electrons or to share electrons with another nonmetal to achieve a complete octet.

Formation of cations An atom’s loss of valence electrons = cation: positively charged ion. Sodium atom, Na, forms a sodium cation, Na+ Calcium atom, Ca, forms a calcium cation, Ca2+ Metals Na 1s22s22p63s1 Lose of valence electron Na+1s22s22p6 Which equals the configuration of Neon Na  Na+ + e-

Formation of anions Anion is an atom or group of atoms with a negative charge The gain of electrons The name of the anion ends in –ide Chlorine atom forms a chloride ion and oxygen atom forms an oxide ion Nonmetals Cl 1s22s22p63s2 3p5 gain of electron Cl- 1s22s22p63s2 3p6 which is equal to the configuration of Ar

Anions continued… Cl + e-  Cl- The ions formed from Group VII A are called halide ions. 7 valence electrons and need to only gain 1 electron to achieve noble gas configuration Charge of 1-

Can u solve it? How many electrons will each element gain or lose in forming an ion? Ca, F, Al, O Write the name and symbol on the ion formed when: potassium atom loses 1 electron, zinc atom loses two electron, fluorine atom gains one electron

Ionic compounds Composed of cations and anions Electrically neutral Held together by ionic bond: attraction between positive cation and negative anion Chemical formula: shows kinds and numbers of atoms (NaCl) Formula unit: lowest whole-number ratio of ions in an ionic compound (Be2O2 = BeO)

Properties of ionic compounds Crystalline solid at room temperature High melting points Conduct an electric current when melted or dissolved in water

Ions Monatomic ion: single Polyatomic ions: composed of more than one Names usually end in –ite or –ate -ite has 1 less oxygen than -ate Charges of the cations of transition metals ions must be determined by the # electrons lost. Form more than one cation with different ionic charges Table 9.2 on page 255

Naming ionic compounds Cation first, name doesn’t change Anion second, remove ending and add –ide for monatomic anions For polyatomic ions use appropriate name from list

Metallic bonds Valence electrons of metal atoms are a sea of electrons Mobile and drift freely from one part of metal to another Metallic bond: attraction of free-floating valence electrons for the positively charged metal ions. Good conductors of electric current because electrons can flow freely in them Malleable/ductile due to mobility of electrons

Alloys Mixtures composed of 2 or more elements, at least one is a metal Properties are often superior to their component elements