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Chemical Bonding What kinds of bonding are there? Chemical Bonding • Electrostatic Force = force existing as a result of the attraction or repulsion between 2 charged particles • Opposites attract; Like repel • Greater distance smaller attractive/ repulsive force (and vice-versa) Atomic Radius Trend • Going from left to right across a given period, the atomic number (no. of p) increases positive charge on the nucleus (nuclear charge) increases. • This means that there is a greater force of attraction for the electrons in the shell and the distance between the electrons and the nucleus decreases. Atomic Radius Trend • Going across the row, atomic radius decreases. • Going down the group, atomic radius increases because the more electrons around the nucleus, the greater the volume needed to contain them (since electrons repel each other and can’t easily be “compacted”. Revisit Shells • Open shell = containing less than its maximum no. of e • Closed shell = containing its maximum no. of e • Valence electrons = electrons in OPEN shells Schematic for No. of Valence Electrons Note • For purposes of this section, only valence electrons are considered for bonding and the transition metals (lanthanides and actinides) are ignored. Lewis Structure • Show how valence electrons are distributed for Ga, As and Kr Lewis Structure What is Valence? • Valence is NOT valence electrons. • Valence of an atom = the number of unpaired electrons. It is sometimes also called the combining capacity. What is Ionization Energy? • In order to form a positive ion, an electron must be removed from a neutral atom. • Ionization energy = the energy required to REMOVE electron from a neutral atom. Ionization Energy Trend • Ionization energy INCREASES across a period (higher positive nuclear charge to attract the electrons, so hard to remove them) • DECREASES down a group since each shell is further from the nucleus (less nuclear charge)