[ CHEM1010 ] Periodic Properties of the Elements

Dmitri Mendeleev

Who is credited with making the first periodic table by arranging elements by mass and properties?

Germanium

Mendeleev was able to predict the existence of yet undiscovered elements, such as Gallium and _____.

Atomic Number

In the modern periodic table, elements are arranged in order of increasing _____.

118 elements

How many total elements are currently recognized in the modern periodic table?

Valence Electrons (Main Group)

The electrons located in the outermost energy shell of an atom.

The outermost d electrons.

In transition elements, which electrons besides those in the outermost shell are included in the valence count?

Core Electrons

What term is used to describe electrons located in lower energy shells beneath the valence shell?

Aufbau

The _____ principle states that energy levels and sublevels fill from lowest energy to highest.

Noble

A short-hand way of writing electron configurations uses the symbol of the previous _____ gas in brackets.

s-block

Identify the orbital block associated with Groups 1A and 2A.

p-block

Identify the orbital block associated with Groups 3A through 8A.

d-block

The transition metals on the periodic table belong to the _____ orbital block.

f-block

The Lanthanide and Actinide series are located in the _____ orbital block.

The energy difference between the ns and (n−1)d sublevels is very small.

Why do some transition metals like Chromium (Cr) have irregular electron configurations?

Zeff​

The net positive charge from the nucleus that attracts a particular electron.

It decreases.

How does atomic radius generally change when moving from left to right across a period?

It increases.

How does atomic radius generally change when moving down a group?

The effective nuclear charge (Zeff​) increases, drawing the valence shell closer.

Why does atomic radius decrease across a period?

The valence shell is located farther from the nucleus in higher energy levels.

Why does atomic radius increase down a group?

The cation is smaller.

How does the size of a cation compare to its neutral parent atom?

The anion is larger.

How does the size of an anion compare to its neutral parent atom?

Isoelectronic Species

Different atoms or ions that possess the same electron configuration.

A larger negative charge results in a larger anion.

Among isoelectronic species, how does an increase in negative charge affect the size of the ion?

Ionization Energy (IE)

The energy required to remove an electron from an atom or ion in the gas phase.

Endothermic

Removing an electron is an _____ process, meaning it requires the input of energy.

It increases.

How does first ionization energy generally change moving from left to right across a period?

It decreases.

How does first ionization energy generally change moving down a group?

It involves removing an electron from a positively charged ion.

Why is removing a second electron (Second IE) harder than removing the first?

5A to 6A

Ionization energy generally increases across a period except for drops between Group 2A to 3A and Group _____.

It is due to the repulsion between paired electrons in the p-orbital.

Why does ionization energy drop when moving from Group 5A to 6A?

Electron Affinity (EA)

The energy change associated with the addition of an electron to a gas-phase atom.

Endothermic (positive)

Although defined as exothermic, the electron affinity for noble gases is actually _____.

The Halogens (Group 7A)

Which group on the periodic table typically has the highest (most negative) electron affinity in any period?

Decreases

Metallic character generally _____ when moving from left to right across a period.

Increases

Metallic character generally _____ when moving down a group.

Core

Sodium (Na) forms a 1+ ion because removing a second electron would require removing a _____ electron.

5

How many valence electrons does Nitrogen (Group 5A) have?

The 4s sublevel

Between 4s and 3d sublevels, which is lower in energy and typically fills first?

They are held most loosely by the nucleus.

Why are valence electrons the most important for chemical bonding?

Covalent radius

Which radius type refers to the bonding radius of an atom?

It remains fairly constant.

What happens to the effective nuclear charge (Zeff​) as you move down a group?

2−

Atoms in Group 6A typically form ions with what charge to match the nearest noble gas?

gain

Nonmetals typically _____ electrons in chemical reactions, meaning they are reduced.

Metallic Character

A measure of how closely an element's properties match the ideal properties of a metal.

They are brittle and dull (nonreflective).

List two physical properties of nonmetals in their solid state.