Write the orbital notation and electron configuration for the following atoms Be B N F Mg

Give the total number of electrons and the identity of the element with the electronic configuration: 1s22s22p63s23p64s23d104p65s2 1s22s22p63s23p4 1s22s22p63s1 1s22s22p63s23p2

2.6 Electron Configuration The electron configuration can be shortened by using Noble Gas Notation. Write the Symbol of the previous Noble Gas, then add the electronic configuration of the additional electrons. Electron Configuration Noble Gas Notation element: nearest noble gas:

2.6 Electron Configuration C. Other Elements Orbital Notation Element Ca 20 electrons 1s 2s 2p 3s 3p 4s Electron Configuration Noble Gas Notation

2.6 Electron Configuration C. Other Elements Orbital Notation Element Cr 24 electrons 1s 2s 2p 3s 3p 4s 3d Noble Gas Notation

2.6 Electron Configuration C. Other Elements As 33 electrons Ar = 18 electrons  Orbital Notation [Ar] 4s 3d 3p Noble Gas Notation

2.6 Electron Configuration C. Other Elements Eu 63 electrons [Xe] = 54 electrons  Orbital Notation [Xe] Noble Gas Notation

2.7 Valence Electrons The chemical properties of an element depend on the number of electrons in the valence shell. The valence shell is the outermost shell (the highest value of n). The electrons in the valence shell are called valence electrons. Be Cl

2.7 Valence Electrons A. Relating Valence Electrons to Group Number Elements in the same group have similar electron configurations. Elements in the same group have the same number of valence electrons. The group number, 1A–8A, equals the number of valence electrons for the main group elements. The exception is He, which has only 2 valence electrons. The chemical properties of a group are therefore very similar.

2.7 Valence Electrons A. Relating Valence Electrons to Group Number Period 1: H 1s1 He 1s2 Period 2: Li 2s1 Be 2s2 B 2s22p1 C 2s22p2 N 2s22p3 O 2s22p4 F 2s22p5 Ne 2s22p6 Period 3: Na 3s1 Mg 3s2 Al 3s23p1 Si 3s23p2 P 3s23p3 S 3s23p4 Cl 3s23p5 Ar 3s23p6

2.7 Valence Electrons B. Electron-Dot Symbols Dots representing valence electrons are placed on the four sides of an element symbol. Each dot represents one valence electron. For 1 to 4 valence electrons, single dots are used. With more than 4 valence electrons, the dots are paired. Element: H C O Cl # of Valence electrons: Electron-dot symbol:

# of Valence electrons: Complete the table Element: N Ge B Te Ba # of Valence electrons: Electron-dot symbol:

2.8 Periodic Trends A. Atomic Size The size of atoms increases down a column, as the valence e− are farther from the nucleus. Increases Decreases The size of atoms decreases across a row, as the number of protons in the nucleus increases, pulling the valence electrons in closer.

2.8 Periodic Trends B. Ionization Energy The ionization energy is the energy needed to remove an electron from a neutral atom. Na + energy Na+ + e– Decreases Ionization energies decrease down a column as the valence e− get farther away from the positively charged nucleus. Increases Ionization energies increase across a row as the number of protons in the nucleus increases.