ch. 5 - periodic law

Question 1

how did Mendeleev group the elements?

Answer 1

organized in order of increasing atomic mass

predicted existence and properties of three remaining elements

Question 2

how did Moseley group the elements?

Answer 2

organized in order of atomic number

Question 3

Periodic Law

Answer 3

the physical and chemical properties of the elements are periodic functions of their atomic numbers

Question 4

modern periodic table

Answer 4

elements w/ similar properties fall in the same group

elements ordered by atomic number

Question 5

how are elements arranged?

Answer 5

vertically in groups, sharing chemical properties

horizontally in periods

Question 6

group 1

Answer 6

alkali metals – soft, reactive, silvery

Question 7

group 2

Answer 7

alkaline-earth metals – less reactive than g1, but still too reactive to be found in pure form in nature

Question 8

hydrogen

Answer 8

unique element; light, reactive, gas

Question 9

helium

Answer 9

special chemical stability

Question 10

group 17

Answer 10

halogens – most reactive nonmetals, react w/ most metals forming salt

Question 11

group 18

Answer 11

noble gasses – stable, usually unreactive, colorless, covalent shells

Question 12

transition elements

Answer 12

d block elements; metallic properties

Question 13

main-group elements

Answer 13

p and s blocks; varying properties

Question 14

p block elements

Answer 14

nonmetals on right
metalloids forming staircase in middle
metals on lower left side – harder and denser than g2 but softer and less dense than d block metals

Question 15

metalloids

Answer 15

semiconductors 
p block (staircase) located between nonmetals and metals

Question 16

f block

Answer 16

between g3 & g4 in 6th and 7th periods
uranium = last naturally occurring element
n-2
lanthanides (first row) = shiny metals similar in reactivity to g2
actinides (second row) = radioactive

Question 17

atomic radii

Answer 17

atomic radius = half the distance between the nuclei of identical atoms bonded together
decreases left to right – increasing positive charge of nucleus, attracting electrons towards it
decreases down to up – decreasing size of electron cloud as sublevels decrease

Question 18

ionization energy

Answer 18

ionization energy = energy required to remove one electron from a neutral atom of an element
ionization - formation of an ion
increases left to right – increasing nuclear charge
increases down to up – more easily removable electrons
loses electron and takes energy

Question 19

electron affinity

Answer 19

electron affinity = energy it takes for an atom to add an electron
increases left to right – increasing nuclear charge
increases down to up – large electron cloud = far electrons from nucleus
gains electron & gives off energy

Question 20

ionic radii

Answer 20

decrease from left to right – electron cloud shrinks

decrease from down to up

Question 21

cation

Answer 21

cation = positive ion

loss of electrons leading to decrease in atomic radius

Question 22

anion

Answer 22

negative ion

addition of electrons increases atomic radius

Question 23

valence electrons

Answer 23

electrons available to be lost, gained, or shared in order to form chemical compounds
often located in incompletely filled main-energy levels

Question 24

electronegativity

Answer 24

ability of an atom to attract electrons
increases from left to right
increases from down to up
higher up = more electromagnetic

Question 25

why is 2nd ionization energy higher than 1st, and so on?

Answer 25

2nd requires more energy to remove electrons

Question 26

define diff ionization energies

Answer 26

1st = remove one electron
2nd = remove two electrons
3rd = remove three electrons

Question 27

of metals and nonmetals, which forms positive ions and which forms negative ions?

Answer 27

metals tend to form positive ions

nonmetals tend to form negative ions

Question 28

is energy released or absorbed when electrons are added?

Answer 28

released

Question 29

is energy released or absorbed when electrons are removed?

Answer 29

absorbed

Question 30

groups vs periods

Answer 30

groups = vertical columns of elements sharing similar properties
periods = horizontal rows of elements (indicating energy sublevels)