Chem Chapter 6: Periodic Tables/Periodic Law

John Newlands

Scientists who grouped elements into groups of 8, called the Law of Octaves

Law of Octaves

A principle for classifying elements by arranging them in order of increasing atomic mass. It states that every eighth element has properties similar to the first, much like the notes in a musical octave

Meyer and Mendeleev share what in common?

Both grouped the elements with atomic mass/elemental properties

Why did Mendeleev get credit for the table?

He published first

How did Mendeleev order the table?

In vertical columns based on their reactivity with other elements, also on atomic mass

What was special about Mendeleev’s table?

There were blank spaces for undiscovered elements

How did Moseley change the periodic table arrangement?

Elements arranged according to atomic number

Periodic Law

Elements are arranged according to repititous properties

Groups in the PT

A vertical column of elements; aka a chemical family

How many groups are on the PT?

18

Period

Horizontal row of elements; 7 periods on the table

Elements in the same period have?

A strong resemblance among their member

List the 4 chemical families:

1. Alkali metals

2. Alkaline earth metals

3. Halogens

4. Noble gases

Alkali Metals (Group, Charge, Examples)

1A, +1, Li/Na…

Alkaline Earth Metals (Group, Charge, Examples)

2A, +2, Be/Mg/Ca

Halogens (Group, Charge, Examples)

7A, -1, Cl/F

Noble Gases ((Group, Charge, Examples)

8A, N/A, Xe/Kr

3 PT Blocks

1. Representative Elements

2. Transition Metals

3. Inner Transition Metals

What block are these elements in?

1. Representative Elements = ?

2. Transition Metals = ?

3. Inner Transition Metals = ?

1. s/p

2. d

3. f

Metals are located?

Around the left side

metals characteristics

• Have luster or shine

• good conductors of heat/electricity

• solid at room temperature

• malleable (thin sheets)

• ductile (fine wire)

non-metals characteristics

• lacks luster; is dull

• poor conductors

• neither malleable/ductile

• many are gases at room temperature (bromine is a liquid)

• varied physical properties

semi-metals location

along the staircase, except for aluminum and polonium

semi-metals are also called?

metalloids

semi-metals’ properties

• properties intermediate of metals/nonmetals

• properties not predictable/different for the different elements

type of electrons

1. valence electrons (outermost)

2. core electrons (remaining)

patterns in different groups (1A, 2A, 7A, 8A)

1. alkali metals end with s¹

2. alkaline earth metals end with s²

3. halogens end with p⁵

4. noble gases end with p⁶

atoms tend to ___ or ____ electrons to becomea stable noble gas

lose or gain

isoelectronic

elements that have the same e-config

for isoelectronic elements

write the configuration using the previous noble gas

which 2 elements are liquid at room temperature?

Mercury (Hg) and Bromine (Br)

atomic radius

distance from the center of the nucleus to the outermost electrons

characteristics of atomic radius

• strong attractive forces between protons/electrons make the atom smaller going from left to right

• electron shielding

electron shielding

inner core electrons’ attraction to protons causes the outer electrons to be held less tightly (size increases top to bottom)

ionic radius

size of the ions

electronegativity

the attraction an atom has for the shared pair of electrons in a bond (pull on electrons)

which group is NOT on the electronegativity table (mostly)

noble gases

ionization energy

energy required to remove 1 mole of electrons from 1 mole of neutral gaseous atoms

2 trends go from left to right, bottom to up

Electronegativity & Ionization Energy

successive ionization energy

energy used to remove successive electrons (2nd/3rd/4th)

Magnesium’s 3rd IE is high because?

It has a noble gas config (easy to remove 1st/2nd however)

anions v. cations

• cations are positively charged, smaller than anions

• anions are negatively charged, bigger than cations