Atoms and molecules
An atom is the smallest unit of a matter. It can not be further divided to obtain smaller particles by any chemical means. Atoms can be subatomic in nature. Subatomic particles are:
- Protons: it consists of particles with a positive charge.
- Neutrons: this type of particles has no charge.
- Electrons: consists of particles with negative charge.
Note that when an atom gains or loses an electrons; it can either be negatively charged or positively charged ion.
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All matters can easily be classified as:
- Elements: it cannot be broken down into other substances.e.g gold, iron, hydrogen, sodium etc. Each element is known for it chemical symbol. E.g gold – Au, iron – Fe etc.
- Compounds: it has to do with the chemical combination of two or more elements.e.g water under room temperature consist of two elements which are hydrogen and oxygen. The chemical symbol for water is H2O.
- Mixtures: it involves physical combination of two or more substances that maintains each of its properties. E.g sand and water is a mixture.
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Atoms are being held together in molecules and compounds by bonds. There are two types of bonds:
- Covalent bond: here atoms share a pair of electrons. And each of the atom contributes to one electron.
- Ionic bond: here atoms gain or lose electrons to become ions. The attraction between the two charges ( positive and negative charge) holds the compound together.
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Questions
1. Atom is the smallest unit of matter that can combine ……….. with other matter?
A. Physically
B. Technically
C. Chemically
D. Definitely
Ans= C
2. Atoms are themselves made of ……… particles?
A. Atomic
B. Small
C. Subatomic
D. Diverse
Ans= C
3. …….. are substance that Cannot be broken down into other substances.
A. Elements
B. Compounds
C. Particles
D. Mixtures
Ans= A
4. Salt water is an example of ………?
A. Bonds
B. Compounds
C. Mixtures
D. Atoms
Ans= C
5. Atoms in molecules or compounds are being held by?
A. Chemical
B. Electron
C. Compounds
D. Bonds
Ans= D