Chapter 7 Trends in the periodic table

Question 1

atomic radius (covalent radius)

Answer 1

half the distance bet. adjacent nuclei of the same element that are joined together by a single covalent bond.

Question 2

trend (AR) down the group

Answer 2

increases (new energy level, screening effect)

Question 3

trend (AR) across period

Answer 3

decreases (increase in effective nuclear charge, no increase in screening effect)

Question 4

factors that influence those trends (AR) (4)

Answer 4

1 - total number of shells 2 - no. of of inner shells with electrons which screen outer ones 3 - size of nuclear charge 4 - whether change in the electron structure is in the outermost shell or not.

Question 5

transition elements (AR)

Answer 5

approx. the same no.

Question 6

isoelectronic ions

Answer 6

same no. of electrons eg; o2- , F- Mg2+ the smallest of these ions is the one with the biggest nuclear charge ie. Mg+

Question 7

Trends(2) in group 1 Alkali Metals + 2 reactions

Answer 7

They will become more reactive going down the group
AR increases down the group , increased screening leading to the outermost electron being loosely held (reactivity) + oxygen = oxides + water = hydroxides

Question 8

Trends in group 7 Halogens

Answer 8

most electronegative elements, great attraction for electrons and often gain electrons in their reactions (quite reactive) decreased reactivity going down the group

Question 9

First Ionization Energy

Answer 9

minimum energy required to remove the most loosely held electron from 1 mole of gaseous atoms in their ground state

Question 10

Trends in Ionization Energy

Answer 10

increase across period (cause AR deceases, effective NC has increased) decrease down a group (inc. in AR, inc. in shielding effect)

Question 11

Exceptions in Trends in Ionization Energy

Answer 11

Half /fully filled sublevels (extra stability)

Question 12

Trends in Ionization Energy values

Answer 12

steady increase, large increase when removed from new sublevel, very large increase when removed from new shell.

Question 13

Electronegativity

Answer 13

relative attraction that an atom in a molecule has for the shared pair of electrons in a single covalent bond

Question 14

Trends in Electronegativity (2)

Answer 14

values increase across period (dec. AR, inc in effective NC ) dec. down a group (inc AR , dec. effectice NC)

Question 15

FIrst ionization energy (equation)

Answer 15

X -> X+ + e-

Question 16

bond length = 1/2 AR

Answer 16

measure bet. the nuclei of atoms gotten by methods of electron diffraction, x-ray diffraction

Question 17

AR for noble gases

Answer 17

none , noble gases don’t form covalent bonds .’. no AR

Question 18

effective nuclear charge

Answer 18

the attractive positive charge of nuclear protons acting on valence electrons. The effective nuclear charge is always less than the total number of protons present
in a nucleus due to shielding effect

Question 19

equation for effective nuclear charge

Answer 19

Zeff = Z – S ( where Z = atomic no. , S = no. of shielding electrons )

Question 20

chemical properties of elements determined by

Answer 20

no. of electrons in the outermost energy level