Inorganic Ch 2

using slaters rule, calculate the effective nuclear charge on an electron in each of the orbitals in an atom of potassium

Effective nuclear charge on 1s = 18.65; 2s/2p = 14.85; 3s/3p = 7.75; 4s = 2.20.

using slaters rule, calculate effective nuclear charge on a 3p electron in a) aluminum and b) chlorine. explain

Effective nuclear charge on 3p electrons in aluminum = 3.50, in chlorine = 6.10. The higher effective nuclear charge on the outermost electrons in chlorine results in that element having the smaller atomic radius of the two and the higher first ionization energy.

define a) second ionization energy

(a) Energy needed to remove the second ground-state electron from an atom (X+ X2+ + e).

define electron affinity

(b) Energy needed to add an electron to the lowest available energy state of an atom.

define betrand's rule

(c) For each essential element, there is a range of intake from too low to optimal to excess.

suggest the number of neutrons in the most common isotope of calcium

20 (because 20 protons and 20 neutrons would give a doubly completed shell nucleus).

suggest why polonium-210 and astatine-211 are the isotopes of those elements with the longest half lives

Both polonium-210 and astatine-211 have 126 neutrons, the filled-shell value, giving additional stability to the isotopes.

which atom should have the larger covalent radius, fluorine or chlorine why

Chlorine. With increasing "layers" of electrons, the effective nuclear charge on the outermost electrons will decrease (even though the actual number of protons has increased). Hence the atom of chlorine will have the greater covalent radius.

which one in each pair - boron and carbon and carbon and nitrogen - will have higher second ionization energy explain

Electron configurations: B = 1s22s22p1; C = 1s22s22p2; N = 1s22s22p3. For carbon and nitrogen, the second ionization energy requires removal of a second 2p electron. Because the 2p electrons of nitrogen experience the higher effective nuclear charge, nitrogen will have the higher second ionization energy. For boron and carbon, the second electron removed from the boron will be a 2s. Although the simplistic Slater‟s rules show the shielding the same as for 2p electrons, in fact the 2s electrons are held more strongly than the 2p. Hence boron will have the higher second ionization energy.

on what basis are elements classified as semimetals

Elements with some chemical and/or physical properties that resemble metals and others that resemble nonmetals. Alternative answer: elements with properties that are intermediate between those expected for a metal and those expected for a nonmetal.

which element, sodium or magnesium should have electron affinity closer to zero explain

Magnesium. With a filled 3s2 set of electrons, magnesium is less likely to accept an electron (which would have to go into the 3p orbitals) than sodium with a 3s1 configuration (the added electron then giving a "full" 3s2 configuration).

which element should give higher ionization eneryg, arsenic or phosphorus

Phosphorus. With increasing "layers" of electrons, the effective nuclear charge on the outermost electrons will decrease (even though the actual number of protons has increased). Hence the atom of arsenic will have the lower ionization energy.

explain why the atomic mass of cobalt is greater than that of nickel even though the atomic number of colbalt is less than that of nickel

The common isotope of cobalt has more neutrons than that of nickel, hence the atomic mass will be higher. In fact, the only natural isotope of cobalt has 32 neutrons, while nickel has two common isotopes, one with 30 neutrons (68 percent), the other with 32 neutrons (26 percent).

why were the names of lanthanised and actinides inappropriate for those series of elements

The ending -ide traditionally is used to identify the anion of an element (fluorine-fluoride), so the suffix is inappropriate for the group of elements themselves.

what part of periodic table contains the elements that we need in large quantities? how does this correspond to abundance

The first four periods of the periodic table (especially the first three periods). This corresponds to the elements of higher abundance (for example, iron is the most abundant of the transition metals, and it is the only transition metal required in large dietary amounts).

why must heavy elements on this planet have been formed from the very early supernovas that exploded

The only way in which high-atomic-number elements can be formed is by means of the energy from supernova explosions (iron is the highest atomic-number element that is formed exothermically by fusion reactions). Hence these elements on this planet must have been formed from such an explosion billions of years ago

suggest why group 11 elements are sometimes called coinage metals

Throughout recorded history, copper, silver, and gold have been used to make coinage. The metals are easy to extract from their ores and have been known for thousands of years. They are unreactive, ensuring a long circulation life for the coins. On the other hand, they are now so expensive that they are no longer used (the current U.S. penny consists of a copper coating over a lower-cost zinc core).

identify the only two radioactive elements to exist in significant quantities on earth. explain why still present

Uranium and thorium. Both of these elements have isotopes with half-lives in the 109-1010 year range; hence a considerable proportion of these elements are still present from their original supernova synthesis (we now know that bismuth only exists as a very long half-life isotope).

suggest reason why the covalent radius of hafnium is less than that of zirconium, the element above it in the periodic table

With the very poorly shielding 4f orbitals having been filled corresponding to the added protons, the effective nuclear charge on the outer (6s and 5d) electrons will be increased; hence the covalent radius will decrease.