chemistry L3

What is a period in the periodic table?

A horizontal row of elements corresponding to filling of a principal energy level.

What is a group in the periodic table ?

A vertical column of elements having similar valence electron configurations and hence similar chemical properties.

How many groups and periods are in the modern table?

18 groups and 7 periods.

what are the elements of the s-block?

elements of group 1 and 2, bc they have their valence electrons in the s orbital

what are the elements of p-block?

elements in groups 3-7 (13-18) because they have their valence electrons in the p orbital

What are transition elements?

d-block elements (Groups 3–12) with partially filled d-orbitals.

What are inner transition elements?

f-block elements (lanthanides and actinides) with partially filled f-orbitals

Define atomic radius.

Half the distance between the nuclei of two identical atoms joined by a single bond

What is covalent radius?

Half the distance between nuclei of two atoms covalently bonded.

What is van der Waals radius?

Half the distance between the nuclei of two non-bonded atoms in adjacent molecules.

What is the trend of atomic radius in the periodic table?

Decreases across a period (due to increasing nuclear charge) and increases down a group (due to addition of shells).

Define ionization energy.

The minimum energy required to remove one mole of electrons from one mole of gaseous atoms or ions

What is the trend of ionization energy?

Increases across a period (due to increasing nuclear charge) and decreases down a group (due to increasing atomic size)

Define electron affinity.

The energy change when one mole of electrons is added to one mole of gaseous atoms to form anions.

Define electronegativity.

The tendency of an atom in a molecule to attract shared electron pairs toward itself.

Which element is most electronegative?

F

What are the types of elements by position in periodic table?

• Metals (left side, electropositive, conductors).

• Non-metals (right side, electronegative, insulators).

• Metalloids (borderline, e.g., Si, As, Sb, Te).

Define metallic and non-metallic character trends.

Metallic character increases down a group, decreases across a period.

Define shielding effect.

The repulsion experienced by outer electrons from inner electrons, reducing the effective nuclear charge.

What is effective nuclear charge (Zeff)?

The net positive charge experienced by a valence electron, given by Zeff = Z - S, where S = screening constant.