أرشيف الوسم : anion

ATOMS THREE POSTULATES OF DALTON’S ATOMIC THEORY 1) An element is composed of identical atoms. 2) Atoms of different elements have different properties. 3) Compounds are atoms of 2 or more elements chemically combined. THE LAW OF CONSERVATION OF MASS During a physical change or reaction, or a chemical reaction, matter is neither created nor destroyed. (Lavoisier – 1777) THE …

Atomic size. The atomic or ionic radius is the size of the atom or the ion of an element and is usually considered as the distance between the nucleus and the outermost shell of the electrons of the atom. Trends in atomic sizes in the periodic table. The atomic size of the elements (atoms) decreases from left to right in …

Compounds Compounds are pure substances that differ from elements because they contain more than one kind of atom. The Law of Definite Composition (or the Law of Definite Proportions) applies to compounds. For example, sodium chloride contains one atom of sodium for each atom of chlorine. Water contains two atoms of hydrogen for each atom of oxygen. It is known …