Chemistry Basics: Elements, Atoms, and Molecules

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Questions and Answers

What is the correct way to represent the ionic compound formed between magnesium and chloride?

Mg2Cl2

MgCl

Mg2Cl

MgCl2 (correct)

Which of the following correctly shows the valency of silver?

1+ (correct)

How should the formula for ammonium hydroxide be written?

N2H4O

NH4OH (correct)

NH4O

NH3OH

Which of the following ions has a valency of 2+?

Zinc Signup and view all the answers

What is the proper representation for the ionic bond between calcium and oxide?

CaO Signup and view all the answers

What is the atomicity of oxygen?

2 Signup and view all the answers

Which of the following represents a diatomic molecule?

Oxygen Signup and view all the answers

Which compound is formed by the elements nitrogen and hydrogen?

Ammonia Signup and view all the answers

What is the combining capacity of an element called?

Valency Signup and view all the answers

What kind of ion is formed when an atom loses electrons?

Cation Signup and view all the answers

Which element has an atomicity of 4?

Phosphorus Signup and view all the answers

What type of molecules do compounds formed from metal and non-metal elements contain?

Ions Signup and view all the answers

What is the molecular composition of hydrochloric acid?

H and Cl Signup and view all the answers

What is the correct symbol for Aluminium?

Al Signup and view all the answers

Which element has an atomic mass of 32 u?

Sulphur Signup and view all the answers

What defines the atomic mass of an element?

It is based on the carbon-12 atom. Signup and view all the answers

Which molecule is considered a molecule of an element?

O2 Signup and view all the answers

Which of the following atomic symbols is written incorrectly?

sUl Signup and view all the answers

How is the atomic mass unit (u) defined?

As 1/12th the mass of a carbon-12 atom. Signup and view all the answers

Which of the following statements about molecules is true?

Molecules can exist independently and maintain all properties of the substance. Signup and view all the answers

What is the atomic mass of Oxygen?

16 u Signup and view all the answers

What is the formula for Calcium hydroxide?

Ca(OH)2 Signup and view all the answers

Which element’s atomic mass is 14 u?

Nitrogen Signup and view all the answers

What is the molecular mass of water (H2O)?

18 u Signup and view all the answers

Which of the following combines to form Magnesium chloride?

Mg and Cl Signup and view all the answers

What does one mole of a substance equal?

6.022 x 10^23 molecules Signup and view all the answers

What is the formula for Carbon tetrachloride?

CCl4 Signup and view all the answers

What is the valency of sulphide in the formula of hydrogen sulphide (H2S)?

2 Signup and view all the answers

What does the law of conservation of mass state?

The sum of the masses of reactants and products remains unchanged. Signup and view all the answers

Which of these is the formula for Sodium nitrate?

NaNO3 Signup and view all the answers

According to the law of constant proportions, what can be said about water?

It is composed of hydrogen and oxygen in a consistent mass ratio. Signup and view all the answers

Which of the following statements is NOT part of Dalton's atomic theory?

Atoms of a given element are always different in mass. Signup and view all the answers

What defines an atom?

A particle that can exist independently and retain chemical properties. Signup and view all the answers

What is the atomic radius of a hydrogen atom in meters?

$10^{-10}$ m Signup and view all the answers

How are the symbols of elements represented?

Symbols are often derived from the element's name or Latin name. Signup and view all the answers

Which of the following is a correct statement about atoms?

Atoms can be subdivided into protons, neutrons, and electrons. Signup and view all the answers

What happens when sodium sulfate reacts with barium chloride according to the law of conservation of mass?

The sum of the masses remains unchanged despite the reaction. Signup and view all the answers

Study Notes

Symbol and Element

Elements are represented by symbols.
Single letter symbols are capitalized.
Two letter symbols are capitalized with the first letter capitalized and the second letter lowercase.

Atomic Mass

The mass of an atom is compared to the mass of a carbon-12 atom.
One atomic mass unit (u) is 1/12th the mass of a carbon-12 atom.
The atomic mass of an element is the average mass of one atom compared to 1/12th the mass of a carbon-12 atom.

Molecule

A molecule is the smallest particle of an element or compound that exists independently and shows all the properties of that substance.
A molecule can consist of two or more atoms.
Atomicity is the the number of atoms present in one molecule.
Molecules of elements can contain one or more atoms of the same element.
Molecules of compounds contain two or more atoms of different elements.

Ions

Ions are charged particles.
Cations are positively charged ions.
Anions are negatively charged ions.
Valency is the combining capacity of an element.

Laws of Chemical Combination

Law of Conservation of Mass: Mass cannot be created or destroyed in a chemical reaction. The total mass of reactants equals the total mass of products.
Law of Constant Proportions: Elements in a compound are always present in a definite proportion by mass.

Dalton's Atomic Theory

Matter is made up of tiny particles called atoms.
Atoms are indivisible and cannot be created or destroyed in a chemical reaction.
Atoms of a given element are similar in mass and properties.
Atoms of different elements have different masses and properties.
Atoms combine in small whole number ratios to form compounds.
In a given compound, the relative number and kind of atoms are constant.

Atom

An atom is the smallest particle of an element.
The atomic radius is measured in nanometers (nm).

Writing Chemical Formulae

Place the symbol of the metal or positive ion on the left.
Place the symbol or formula of the non-metal or negative ion on the right.
Write the valencies below the symbols.
Cross over the valencies.
Polyatomic ions should be enclosed in brackets before writing the formula.

Molecular Mass and Formula Unit Mass

The molecular mass is the sum of the atomic masses of all the atoms in a molecule.
Molecular mass is expressed in atomic mass units (u).

Mole Concept

A mole of a substance contains 6.022 x 10^23 particles (atoms, molecules, or ions).
This number is called Avogadro's Number or Avogadro's Constant.
A mole represents a definite mass of a substance equal to the gram atomic mass of an element or the gram molecular mass of a compound.
Gram atomic mass is the atomic mass expressed in grams.

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Description

This quiz covers fundamental concepts in chemistry, including atomic mass, molecular structure, and the characteristics of ions. Test your understanding of how elements are represented by symbols and the differences between cations and anions. Perfect for students looking to solidify their knowledge of introductory chemistry.