krit.club logo

Language of Chemistry - Symbols of Elements

Grade 7ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

A symbol is the short-hand representation of an atom of a specific element. For example, the symbol for Hydrogen is HH.

•

Modern symbols are based on the system proposed by J.J. Berzelius, using the first letter or the first and another letter of the element's name.

•

The first letter of a symbol is always written in Uppercase (Capital), and the second letter is always written in Lowercase. Example: CoCo for Cobalt and MgMg for Magnesium.

•

Some elements derive their symbols from Latin names: Sodium is NaNa (NatriumNatrium), Potassium is KK (KaliumKalium), Iron is FeFe (FerrumFerrum), Copper is CuCu (CuprumCuprum), and Gold is AuAu (AurumAurum).

•

Atomicity is defined as the number of atoms present in one molecule of an element.

•

Monoatomic elements exist as single atoms, such as Noble gases like Helium (HeHe) and Neon (NeNe).

•

Diatomic elements consist of two atoms per molecule, such as Hydrogen (H2H_2), Oxygen (O2O_2), and Nitrogen (N2N_2).

•

Polyatomic elements consist of more than two atoms, such as Phosphorus (P4P_4) and Sulphur (S8S_8).

📐Formulae

Atomicity=Molecular MassAtomic Mass\text{Atomicity} = \frac{\text{Molecular Mass}}{\text{Atomic Mass}}

Representation of a molecule: Xn (where X is the symbol and n is the atomicity)\text{Representation of a molecule: } X_n \text{ (where } X \text{ is the symbol and } n \text{ is the atomicity)}

Total atoms in mXn=m×n\text{Total atoms in } mX_n = m \times n

💡Examples

Problem 1:

Write the symbols for the following elements: Calcium, Chlorine, Silver, and Mercury.

Solution:

Calcium: CaCa, Chlorine: ClCl, Silver: AgAg, Mercury: HgHg.

Explanation:

Calcium and Chlorine use the first and second/third letters. Silver (ArgentumArgentum) and Mercury (HydrargyrumHydrargyrum) use their Latin names.

Problem 2:

Identify the atomicity of the following: O2O_2, O3O_3, and HeHe.

Solution:

O2O_2 is Diatomic, O3O_3 is Triatomic, and HeHe is Monoatomic.

Explanation:

Atomicity is determined by the subscript following the symbol. O2O_2 has 2 atoms, O3O_3 has 3 atoms, and HeHe has 1 atom.

Problem 3:

How many atoms of Oxygen are present in 55 molecules of O2O_2?

Solution:

1010 atoms.

Explanation:

Using the formula m×nm \times n, where m=5m=5 (molecules) and n=2n=2 (atomicity), we get 5×2=105 \times 2 = 10 atoms of OO.

Symbols of Elements Class 7 Notes & Examples | ICSE Science