1. State the difference between the three electrons in Li (Z-3)?. 2. Give the el

Question

1. State the difference between the three electrons in Li (Z-3)?. 2. Give the electron configurations for the following elements: Na (Z-11), Ca (Z-20), Cr (Z-24), Cu (Z-29), Ga (Z-31), Br (Z-35) 3. Which of the molecules below can form H-bonds? Explain NaCl, CH4, NH3, CH3OH, HCI, AlH3 4. What type(s) of bonding would be expected for each of the following materials: Bronze, NaF, HF, BeC12, Polyethylene, Polylactic acid, Wood, Diamond and Tungstern 5. How many molecules are there in 10 gr of a solution containing 1 gr NaCl and 9 gr water?. He 2.1 Li Be 1.0 16 Na Mg 2.0 2.5 3.0 3.5 4.0 Al Si PS CI Ar 1.5 1.9 2.2 2.6 3.0 0.9 1.3 0.8 1.014 1.5 1.6 1.7 1.51.8 1.9 1.9 1.9 16 18 2.0 2.2 2.6 2.8 Rb Sr Y Zr Nb Mo Te Ru Rh Pd Ag CdIn Sn Sb Te Xe 0.8 0.9 1.2 1.3 1.6 2.2 1.9 2.2 2.3 2.2 1.9 1.7 18 2.0 2.1 2.1 2.5

Explanation / Answer

1. The first two electrons reside in the first shell (ie K shell) and the third one is in the L shell, which is the valence shell of the atom. The first two electrons are called the core electrons which do not participate in the bonding where as the valence electron chemical reaction involves the valence electrons.

2. Na (Z= 11): 1s22s22p63s1.

Ca (Z=20):1s22s22p63s23p64s2

Cr (Z=24):1s22s22p63s23p63d54s1

Cu (Z=29):1s22s22p63s23p64s13d10

Ga (Z=31):1s22s22p63s23p63d104s24p1

Br (Z= 35):1s22s22p63s23p64s23d104p5

3. CH3OH can form hydrogen bonds because of the presence of O and H. To form the hydrogen bond the molecule has to be covalent and possess electronegative O or F with hydrogen atom.

4

Bronze - Metallic bonding

NaF - Ionic bonding

HF- Covalent bonding

BeCl2 - Covalent bonding

Polyethylene - Covalent bonding

Polylactic acid - Covalent bonding

Wood - Covalent bonding and intermolecular interactions

Diamond - Covalent bonding

Tungsten - Metallic

5.

58.5 g of NaCl contain 1 mole of NaCl

10g of NaCl contain 0.171 moles of NaCl

one mole of NaCl contain 6.023x1023 entities of NaCl

0.171 mole corresponds to 6.023x1023 x 0.171 = 1.03x1023 molecules of NaCl

18 g of water contain 1 mole of water

9g of NaCl contain 0.5 moles of water molecules

one mole of water contain 6.023x1023 molecules of H2O

0.5 mole corresponds to 6.023x1023 x 0.5 = 3.011x1023 molecules of NaCl

So totally 4.041x1023 entities are present in the solution

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