10 Chem Chapter 5 The Periodic Table

The Periodic Table Reading the Periodic Table -

The modern periodic table has 112 squares The element symbol is in the center of the square The atomic number is above the element symbol on the square The atomic mass is below the element’s symbol on the square The electron configuration is under the atomic mass in the square

Elements with similar properties are aligned in vertical columns called groups or families Horizontal rows on the table are called periods The periodic table has 7 periods and 18 labeled groups Labeling and Naming Groups The IUPAC (International Union of Pure and Applied Chemistry) proposed that the groups be designated by the numerals 1 through 18 The groups at the left and right sides of the periodic table show particularly strong resemblances among their members, so they are frequently referred to by family names. Group 1A are called the alkali metals Group 2A are called the alkaline earth metals The elements in group 7A are called halogens The elements in group 18 are called the noble gases Metals, Nonmetals, and Semimetals Metal -

Have a characteristic of luster or shine Good conductors of heat and electricity Typically solids at room temperature Most metals are malleable

Nonmetals -

Do not possess metallic luster Most are poor conductors

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Many are gases at room temperature, some are solid Some are colored while others are not, some exist as soft solids and others form hard solids Carbon (Diamond) is the hardest natural substance found on earth

Semimetals -

Also called metalloids Share some properties of metals and some of nonmetals

Electron Configuration and the Periodic Table -

Valence Electrons are responsible for an atom’s chemical behavior and are its outermost electrons To write abbreviated electron configurations, we write the symbol of the nearest noble gas with the lower atomic number and the valence electrons that the noble gas has

The – Block Elements The s-block elements -

Composed of Hydrogen, helium , and elements of groups 1A and 2A The s-block contains groups that can hold a maximum of 2 electrons

The p-block elements -

The p-block is 6 elements wide because p orbital can hold up to 6 electrons P-block lasts from group 3A to group 8A

The d-block elements -

This block takes up the middle of the table The d-block can hold up to 10 electrons

The f-block elements -

The 28 elements placed below the main body of the periodic table Also known as the inner transition metals

Periodic Trends

Atomic Radius -

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The atomic radius is the distance from the center of an atom’s nucleus to its outermost electron Atoms get larger going down a group. This is because the principal quantum number of the outermost electrons increases. Electrons with a larger principal quantum number are found in orbital that extend farter away from the nucleus, which makes the atomic radius larger. Atoms get smaller moving from left to right across each period. The outer electrons of atoms (left to right) are increasing attracted to the nucleus. A stronger attractive force shrinks the electrons’ orbital and makes the atom smaller.

Ionization Energy -

An atom’s ionization energy is the energy needed to remove one of its electrons Ionization energy is a reflection of how strongly an atom holds onto its outermost electron Ionization energies decrease as you move down a group Ionization energies increase as you move from left to right across a period

Successive Ionization Energies -

The energy required to remove the first electron from an isolated atom is called the first ionization energy(or simply ionization energy) In order to remove electrons beyond the first electron, it is called second ionization energy, third ionization energy for the third electron, and so forth Ionization energies show that an atom holds the electrons in its noble gas inner core much more strongly that it holds its valence electrons

Electron Affinity -

Electron Affinity is the energy change that occurs when it gains an extra electron There isn’t a specific trend for electron affinity unless you look that their electron configurations Using both electron affinity and ionization energies you can gain an important principle about atoms, a principle that is the octet

rule which states that atoms tend to gain , lose, or share electrons in order to acquire a full set of valence electrons Electronegativity -

An atom’s electronegativity reflects its ability to attract electrons in a chemical bond. The least electronegative elements are fin the lower left corner of the periodic table An atom’s electronegativity is related to its ionization energy and electron affinity Increases as you move from left to right across a period and decrease as you move down a group