Basic Chemistry: Elements, Atomic Structure, and the Periodic Table

Element

The simplest form of matter; pure substances from which all other things are built.

Chemical symbols

Abbreviations that represent names of elements, consisting of one or two letters with the first letter capitalized.

C

Chemical symbol for carbon.

O

Chemical symbol for oxygen.

He

Chemical symbol for helium.

Au

Chemical symbol for gold, derived from its Latin name.

Ag

Chemical symbol for silver, derived from the Latin word 'argentum'.

K

Chemical symbol for potassium, derived from the Latin word 'kalium'.

Na

Chemical symbol for sodium.

Fe

Chemical symbol for iron.

Cu

Chemical symbol for copper.

Periodic Table

Organizes 118 elements in order of increasing atomic mass, with groups containing elements with similar properties.

Group 1A

The alkali metals, including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), which are very reactive with water.

Group 7A

The halogens, including fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), which are diatomic molecules in their elemental form.

Group 8A

The noble gases, including helium (He), neon (Ne), and argon (Ar), which are colorless, odorless, and unreactive.

Metals

Elements that are shiny, ductile, and good conductors of heat and electricity.

Nonmetals

Elements that are dull, brittle, and poor conductors, serving as good insulators.

Metalloids

Elements that are so-so conductors, used as semiconductors and insulators.

Diatomic molecules

Molecules consisting of two atoms, such as I2, Br2, Cl2, and F2.

Atomic mass

The mass of an atom, which increases from left to right across a period in the periodic table.

Group numbers

Written at the top of each vertical column in the periodic table, indicating the classification of elements.

Study Check

A prompt to identify elements based on their group and period.

Atom

the smallest particle of an element that retains the characteristics of that element.

Subatomic particles

The particles inside an atom.

Protons

positive (+) charge.

Electrons

negative (-) charge.

Neutrons

neutral charge.

Rutherford Experiment

showed that an atom consists of most empty space and contains a dense nucleus that holds the protons and neutrons.

Atomic mass unit (amu)

a small unit of mass used by chemists.

Mass of a proton

1.67 x 10-24 g.

Atomic number

the number of protons present in EVERY atom of a specific element.

Mass number

the total number of protons AND neutrons in an atom.

Neutral atom

an atom where the net charge is zero.

Net charge in a neutral atom

number of (+) protons = number of (-) electrons.

Example of neutral aluminum atom

The atomic number for Al is 13, so every Al atom has 13 protons and 13 electrons.

Mass number calculation

protons + neutrons = mass number.

Neutrons calculation

neutrons = mass number - atomic number (protons).

Lead (Pb) mass number

A neutral atom of lead (Pb) has a mass number of 207.

Characteristics of elements

Atoms of an element are similar to each other and different from those of other elements.

Electrons mass

An electron has a very small mass, 0.000 549 amu.

Proton mass

A proton has a mass of about 1 (1.007) amu.

Neutron mass

A neutron has a mass of about 1 (1.008) amu.

Identifying feature of an element

The atomic number is the identifying feature for that element.

Charge of protons and electrons

Protons are (+) and electrons are (-).

Protons in the nucleus

82

Neutrons in the nucleus

207 - 82 = 125 neutrons

Electrons in the atom

82 electrons (an atom is neutral, so the number of electrons = the number of protons)

Mass number of ruthenium (Ru)

106

Isotopes

Atoms of the same element that have a different number of neutrons

Mass number formula

Mass number = protons + neutrons

Isotope symbol for oxygen (O)

16 O with 8 protons, 8 neutrons, and 8 electrons

Isotope symbol for phosphorus (P)

31 P with 15 protons, 16 neutrons, and 15 electrons

Isotope symbol for zinc (Zn)

65 Zn with 30 protons, 35 neutrons, and 30 electrons

Valence electrons

Electrons present in the outermost energy level, involved in chemical bonding

Group number and valence electrons

The group number gives the number of valence electrons for the representative elements

Electron-dot symbols

Represent an atom's valence electrons as dots placed on the top, bottom, and sides of a chemical symbol

G. N. Lewis

The first to use valence electrons to explain chemical bonding

Arrangement of 1-4 valence electrons

Arranged as single dots around the atoms; no electrons are paired

Example of valence electrons in aluminum (Al)

Al has 3 valence electrons

Arrangement of 5-8 valence electrons

One or more of the electrons is paired

Example of valence electrons in nitrogen (N)

N has 5 valence electrons

Atomic symbol for an atom with 17 protons, 20 neutrons, and 17 electrons

Atomic symbol is 37 Cl

Atomic symbol for an atom with 47 protons, 60 neutrons, and 47 electrons

Atomic symbol is 107 Ag