Chapter 3-Atoms and Molecules

________= given mass of compound /sum of mass numbers of the elements present in a compound.

Mole

Compound molecules

________ are created when specific proportions of atoms from several elements combine.

Metals

________ and some other elements, such as carbon, do not have a simple structure but consist of a very large and indefinite number of atoms bonded together.

An atom consists of a(n) ________ that is surrounded by one or more negatively charged electrons.

central nucleus

A(n) ________ is a particle of matter that uniquely defines a chemical element.

atom

helium

Many elements have only one atom per molecule, including ________ (He), argon (Ar), and others.

constituent particles

Positively charged sodium ions (Na+) and negatively charged chloride ions (Cl)- make up its ________.

________ can be used to find out how the atoms of an element will combine with the atom (s) of another element to form a chemical compound.

Valency

chemical reactions

Atoms, the incredibly small building blocks of all matter, take part in ________.

A negatively charged ion is called ________

anion

Atomic radius

________ is measured in nanometres.

Atoms

________ create ions and molecules.

different elements

A molecule can be created by joining together atoms of the same element or of ________.

________ are created when atoms join in a ratio of small whole numbers.

Compounds

A(n) ________ is an association of charged atoms.

polyatomic ion

The ________ was the most astonishing idea Dalton's atomic theory provided.

atomic mass

chemical reaction

In a(n) ________, atoms can not be formed or destroyed since they are indivisible particles.

Eg In a compound such as water, the ratio of the mass of hydrogen to the mass of oxygen is always 1

8, whatever the source of water

Carbon dioxide (CO2 ) Carbon, Oxygen 3

8

Ammonia (NH3 ) Nitrogen, Hydrogen 14

3

Water (H2O) Hydrogen, Oxygen 1

8

Its formula unit mass can be calculated as

1 × 23 + 1 × 35.5 = 58.5 u

During a chemical reaction, the sum of the _________ of the reactants and products remain unchanged.

Masses

Ionic compounds are formed by the combination between ________ an ______.

Metal and non- metals

Mole is a link between the __________ and __________.

Mass of atoms & number of atoms

Those ions which are formed from single atoms are called _________.

simple ions

In a pure chemical compound, elements are always present in a ________ proportion by mass.

definite

The SI unit of amount of a substance is __________.

mole

The valency of an ion is _________ to the charge on the ion.

equal

The abbreviation used for length names of elements are termed as their _______.

symbol