Periodic Trends

Periodic Trends

By: M. Silverman

Origin of the Periodic TableIts organization began with the work of the Russian chemist Dmitri Ivanovich Mendeleev (1834-1907), and was published in 1869.

The Modern Periodic Table

• In 1914 Henry Moseley re-sequenced the periodic table by atomic charge rather than mass.

• Around 1943 Glen Seaborg discovered the Actinides.• During the early and mid twentieth century, Neils

Bohr and others explained the periodic trends of elements with the Quantum Theory.

[He] 2s2 2p2 Nobel Gas Configuration

Rows = Periods or Energy level of valence electronsColumns = Groups or Families of Elements with similar

properties.

Major DivisionsNonmetalsAt room temperature:

SolidsLiquidsGases

Metals

Metalloids

Periodic Properties: Major Groups

Why? The Answer is Valence!

s1 s2 s2p1 s2p5s2p3 s2p4s2p2 s2p6

Group TrendsMetal vs. nonmetal• Metal: most solid at room temperature, shiny,

malleable, ductile, good conductor of heat and electricity, shiny, often grey, silver, or yellowish in color, more reactive, form positive ions.

• Nonmetal: Often gases at room temp., dull, brittle, poor conductors, lower reactivity, form negative ions.

Reactivity: How readily an element reacts with other elements.

K Cu W

S

Cl

Si

• Each period following the first period also begins with a group 1 metallic element and ends with a noble gas.

• Metalloids separate metals from nonmetals and are in between in properties and thus known as “semiconductors”.

Learn these group names!

Chalcogens

Period Trends: Atomic Radius• Atomic radius: the distance from the nucleus to the outer

edge of the electron cloud.

Period Trends: Ionization Energy• Ionization energy: the energy needed to remove

an electron from a neutral atom.

Period Trends: Electron Affinity• Electron Affinity: The energy change that occurs

when an electron is acquired by a neutral atom.

Period Trends: Electronegativity• Electronegativity: a measure of the ability of an atom in a

chemical compound to attract electrons from another atom in the compound. This scale was invented by Nobel Chemist Linus Pauling and does not measure actual energy in kJ.

SC.A.2.4.5 Sample MC Item7. Ionization energy is the energy required to remove an electron from an atom in the gas phase. In the graph below, the ionization energy is shown as a function of the atomic number for the first 20 elements of the periodic table.

The elements 3, 11, and 19 require the lowest amount of ionization energy. What do the elements with atomic numbers 3, 11, and 19 have in common?

A. They have one electron in their outer orbital. B. They lose a proton, which makes them neutral. C. They have seven electrons in their outer orbital. D. They have an extra proton, which makes them neutral.

★

A

The End