Chapter 2:Atoms and Periodic table

Atom

________ is the smallest part of an element.

brittle solids

Eleven are gases at room temperature, six are ________, and one is a liquid.

Chemical reactions

________ change only the way that atoms are combined in compounds.

Russian chemist

In 1869, the ________ Dmitri Mendeleev organized the elements in order of increasing mass and then organized elements into groups based on similarities in chemical behaviour.

neutrons

The protons and ________ are packed closely together in a dense core called the nucleus.

spin

Each orbital can hold only two electrons, which differ in a property known as ________.

Z

Each atom has a specific number of protons, neutrons, and electrons, and the identity of the element is determined by the number of protons within the nucleus, also called the elements atomic number (________)

→The metalloids

________ are located in a zigzag band between the metals on the left and non- metals on the right side of the periodic table.

→18 elements

________ are non- metals.

Bromine

________ is the only liquid non- metal.

→Group 7A Halogens

________: Fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At) are colourful and corrosive non- metals.

metals aluminum

→ 94 are classified as ________, gold, copper, and zinc, for example.

periodic table

The ________ can be divided into four regions, or blocks, of elements according to the electron shells and subshells occupied by the subshell filled last.

valence electrons

Because the ________ are the most loosely held, they are the most important in determining an elements properties.

Atoms

________ are composed of tiny subatomic particles called protons, neutrons, and electrons.

→RULE

________ 2: Each orbital can hold only two electrons, which must be of opposite spin.

Group 1A-Alkali metals

Lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) are shiny, soft metals with low melting points

Group 2A-Alkaline earth metals

Beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) are also lustrous, silvery metals but are less reactive than their neighbours in group 1A

Group 7A-Halogens

Fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At) are colourful and corrosive non-metals

Group 8A-Noble gases

Helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) are colourless gases

Within shells, electrons are further grouped into subshells of four different types, identified in order of increasing energy by the letters s, p, d, and f. The first shell has only one subshell, s. The second shell has two subshells

an s subshell and a p subshell

→RULE 1

Electrons occupy the lowest-energy orbitals available, beginning with 1s

→RULE 2

Each orbital can hold only two electrons, which must be of opposite spin

→RULE 3

Two or more orbitals with the same energy are each half-filled by one electron before any one orbital is completely filled by the addition of the second electron

three isotopes of hydrogen

protium, deuterium, tritium.

atomic mass number (A)

The sum of the protons and neutrons

isotopes

Atoms with identical atomic numbers but different atomic mass