Atoms and Molecules
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Questions and Answers

What is the ratio of hydrogen to oxygen atoms in a water molecule?

  • 2:2
  • 1:1
  • 2:1 (correct)
  • 1:2

Helium is a diatomic element.

False (B)

What is a negatively charged ion called?

anion

A molecule of water is made up of two hydrogen atoms and one ____ atom.

<p>oxygen</p> Signup and view all the answers

Match the following particles with their charges:

<p>Anion = Negatively charged Cation = Positively charged Sodium ion (Na+) = Cation Chloride ion (Cl-) = Anion</p> Signup and view all the answers

Which of the following is a polyatomic element?

<p>Sulphur (A)</p> Signup and view all the answers

Sodium chloride (NaCl) consists of only negatively charged ions.

<p>False (B)</p> Signup and view all the answers

What type of molecules are formed by atoms of different elements joining together in definite proportions?

<p>molecules of compounds</p> Signup and view all the answers

What does the law of conservation of mass state?

<p>Mass can neither be created nor destroyed. (D)</p> Signup and view all the answers

Lavoisier is known for establishing the law of constant proportions.

<p>False (B)</p> Signup and view all the answers

Who presented the atomic theory in 1808?

<p>John Dalton</p> Signup and view all the answers

The law of constant proportions states that a compound is composed of elements in _____ proportions.

<p>fixed</p> Signup and view all the answers

Match the chemists with their contributions:

<p>Antoine Lavoisier = Law of conservation of mass John Dalton = Atomic theory Joseph Proust = Law of constant proportions Robert Boyle = Experimental method in chemistry</p> Signup and view all the answers

What is a fundamental concept of Dalton's atomic theory?

<p>All matter is composed of atoms. (D)</p> Signup and view all the answers

According to Dalton, compounds are composed of only one type of atom.

<p>False (B)</p> Signup and view all the answers

What should be done to prevent the contents of the flask from escaping during a reaction?

<p>Put a cork on the mouth of the flask</p> Signup and view all the answers

Who postulated the idea of indivisible particles called 'Parmanu'?

<p>Maharishi Kanad (B)</p> Signup and view all the answers

Lavoisier conducted his research in the era of ancient Indian philosophers.

<p>False (B)</p> Signup and view all the answers

What is the meaning of the term 'atom' as introduced by Democritus?

<p>indivisible</p> Signup and view all the answers

The ____________ law states that mass is conserved in a chemical reaction.

<p>law of conservation of mass</p> Signup and view all the answers

Match the philosophers with their contributions:

<p>Maharishi Kanad = Proposed the smallest particles 'Parmanu' Pakudha Katyayama = Elaborated on Kanad's doctrine Democritus = Introduced the concept of 'atom' Joseph L. Proust = Worked on experimental validations</p> Signup and view all the answers

What did Pakudha Katyayama elaborate on?

<p>The doctrine of combined form of particles (A)</p> Signup and view all the answers

Maharishi Kanad suggested that dividing matter would eventually lead to particles that could be divided further.

<p>False (B)</p> Signup and view all the answers

Name one pair of substances listed under X and Y that can be prepared as a 5% solution.

<p>copper sulphate and sodium carbonate</p> Signup and view all the answers

What is the formula for sodium sulphate created by criss-crossing the valencies of ions?

<p>Na2SO4 (B)</p> Signup and view all the answers

A sodium ion has a valency of +1.

<p>True (A)</p> Signup and view all the answers

What is the formula for sodium phosphate?

<p>Na3PO4</p> Signup and view all the answers

The formula for sodium sulphate is Na2______.

<p>SO4</p> Signup and view all the answers

Match the following ions with their valencies:

<p>Na+ = +1 SO4^2- = -2 PO4^3- = -3 Cl- = -1</p> Signup and view all the answers

What is the symbol for the ammonium ion?

<p>NH4+ (B)</p> Signup and view all the answers

Potassium ion has a valency of 2.

<p>False (B)</p> Signup and view all the answers

What is the formula for calcium oxide?

<p>CaO</p> Signup and view all the answers

The symbol for iron (III) ion is ______.

<p>Fe3+</p> Signup and view all the answers

Match the following elements with their respective symbols:

<p>Sodium = Na+ Magnesium = Mg2+ Zinc = Zn2+ Copper (II) = Cu2+</p> Signup and view all the answers

Which of the following compounds is formed with a metal and a non-metal?

<p>Calcium Chloride (A)</p> Signup and view all the answers

Magnesium ion is represented as Mg2-.

<p>False (B)</p> Signup and view all the answers

What charge do phosphate ions carry?

<p>3-</p> Signup and view all the answers

What defines a molecule?

<p>The smallest particle of an element or compound capable of independent existence (C)</p> Signup and view all the answers

Polyatomic ions can exist independently and do not carry any charge.

<p>False (B)</p> Signup and view all the answers

What is the chemical formula of magnesium chloride?

<p>MgCl2</p> Signup and view all the answers

A sample containing 0.144 g of oxygen and 0.096 g of boron has a total mass of ______ g.

<p>0.24</p> Signup and view all the answers

Which of the following represents the main factor in determining the chemical formula of a molecular compound?

<p>Valency of each element (C)</p> Signup and view all the answers

Match the following compounds with their chemical formulae:

<p>Quick lime = CaO Hydrogen bromide = HBr Baking powder = NaHCO3 Potassium sulphate = K2SO4</p> Signup and view all the answers

Calculate the molar mass of ethyne, C2H2.

<p>26 g/mol</p> Signup and view all the answers

Ionic compounds are formed by the sharing of electrons between atoms.

<p>False (B)</p> Signup and view all the answers

Flashcards

Atomicity of elements

Atomicity of an element is the number of atoms present in the simplest molecule of an element.

Monoatomic element

Elements that exist as single atoms.

Diatomic element

Elements that exist as two atoms bonded together.

Polyatomic element

Elements that exist as more than two atoms bonded together.

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Molecule of compound

A molecule formed when atoms of different elements join together in fixed proportions.

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Ion

A charged species (atom or group of atoms) with a net positive or negative charge.

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Anion

A negatively charged ion.

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Cation

A positively charged ion.

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Law of Conservation of Mass

Mass is neither created nor destroyed in a chemical reaction.

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Law of Constant Proportions

Compounds always contain the same elements in the same proportion by mass regardless of their source or preparation.

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Chemical Reaction

A process where substances rearrange to form new substances.

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Element

A substance made up of only one type of atom.

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Compound

A substance made up of two or more elements chemically combined in a fixed ratio.

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Antoine Lavoisier

Scientist who established crucial laws of chemical combination.

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John Dalton's Atomic Theory

Matter is composed of small, indivisible particles called atoms.

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Ancient Indian philosophy

Early ideas about matter's divisibility, suggesting the existence of smallest particles called "Parmanu".

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Ancient Greek philosophy

Early ideas about matter's composition, proposing indivisible particles called "atoms".

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Parmanu

The smallest particles of matter (according to ancient Indian philosophy).

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Atoms

Indivisible particles of matter (according to ancient Greek philosophy).

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Experimental validation

Using experiments to prove or disprove theories about matter.

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Chemical solutions

Homogenous mixtures of a solid (solute) and a liquid (solvent).

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What is an atom?

The smallest unit of an element that retains the chemical properties of that element. It cannot exist independently under normal conditions.

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What is a molecule?

The smallest unit of an element or compound that can exist independently and still retain the properties of the substance.

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Chemical Formula

A representation of a compound that shows the types and numbers of atoms present in a molecule of the compound.

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Polyatomic Ions

Groups of atoms that act as a single unit and carry a fixed charge.

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Valency

The combining capacity of an atom, determined by the number of electrons an atom can gain, lose, or share to achieve a stable electron configuration.

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What is a chemical formula used for?

To represent the composition of a compound and the number of each type of atom present in a molecule.

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Ionic Compound Formula

Determined by the charges of the ions involved, ensuring the overall charge of the compound is neutral.

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Molecular Compound Formula

Based on the valencies of the constituent elements. The formula reflects the simplest whole-number ratio of atoms in the molecule.

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Writing a Chemical Formula

When writing a chemical formula, the valencies or charges of the ions must balance. The metal is written first, followed by the non-metal. For example, in calcium oxide (CaO), calcium is the metal and oxygen is the non-metal.

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Symbol of a Polyatomic Ion

The symbol for a polyatomic ion includes the symbols of the atoms making up the ion, along with its charge.

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Non-metal

An element that typically exists as a gas or solid at room temperature, and is not a metal.

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Metal

An element that is typically shiny, malleable, and ductile, and conducts electricity and heat well.

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What is a chemical formula?

A symbolic representation of the composition of a compound, showing the types and number of atoms of each element present.

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How to write a chemical formula using valencies?

You can represent the valencies of elements with symbols and then combine ions to create a formula that reflects the balance of charges.

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Sodium Phosphate Formula

Na3PO4

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What is the valency of an element?

The combining capacity of an element, which is determined by the number of electrons it can gain, lose, or share to form a chemical bond.

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Symbol and Valency in Formulae

Symbols represent elements, valencies represent their combining capacity. We use them to write chemical formulae.

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Study Notes

Ancient Indian and Greek Philosophers

  • Philosophers questioned the nature of matter and its divisibility
  • Indian philosopher Kanad proposed that matter could be divided into smaller and smaller particles (parmanu) until indivisible particles were reached
  • Greek philosophers Democritus and Leucippus suggested atoms (indivisible particles)

Law of Conservation of Mass

  • Lavoisier and Proust's experiments led to the law
  • Mass is neither created nor destroyed in a chemical reaction

Law of Constant Proportions

  • The ratio of masses of elements in a compound is constant
  • This ratio is independent of the source or method of preparation

Dalton's Atomic Theory

  • All matter is composed of atoms
  • Atoms are indivisible and indestructible
  • Atoms of the same element are identical in mass and properties
  • Atoms combine in whole number ratios to form compounds
  • Relative atomic mass was defined using the ratios determined in chemical reactions

Atomic Symbols

  • The first letter of a symbol is always uppercase
  • The second letter of a symbol, if any, is lowercase
  • Symbols are derived from the name of the element, sometimes from the color, or Greek, Latin or German name

Atomic Mass

  • The relative atomic mass is the mass of an atom relative to 1/12th the mass of a carbon-12 atom

Molecules

  • Molecules are groups of two or more atoms chemically bonded together
  • They represent the smallest particle of an element or compound capable of independent existence
  • Molecule can be composed the same atom type or different atom types

Molecular Mass

  • The molecular mass is determined by adding the atomic masses of all atoms in a molecule

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Description

Explore the foundations of atomic theory in this quiz covering ancient Indian and Greek philosophies, the law of conservation of mass, the law of constant proportions, and Dalton's atomic theory. Test your knowledge on the contributions of philosophers like Kanad, Lavoisier, and Proust.

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