Chap 02 Part 4 Elements, Compounds

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Questions and Answers

Which characteristic uniquely defines non-metals compared to metals?

Produce a resonating sound

Brittle and not ductile (correct)

Good conductors of heat and electricity

Malleable and ductile

Which of the following elements is classified as a metalloid?

Iron

Sodium

Helium

Silicon (correct)

What is a common property of noble gases?

They are reactive with halogens.

They conduct electricity well.

They are inert and unreactive. (correct)

They readily form compounds.

Which of the following elements is not a metal?

Boron Signup and view all the answers

What is the significance of graphite among non-metals?

It is a good conductor of heat and electricity. Signup and view all the answers

Which statement accurately describes an element?

An element is a pure substance containing only one kind of atom. Signup and view all the answers

What distinguishes pure substances from impure substances?

Pure substances consist of only one type of particle. Signup and view all the answers

Which of the following accurately describes the nucleus of an atom?

The nucleus contains protons and neutrons, but no electrons. Signup and view all the answers

Which particle is negatively charged and orbits around the nucleus of an atom?

Electron Signup and view all the answers

Which of the following is classified as an impure substance?

Milk Signup and view all the answers

What is the smallest unit of an element that can participate in chemical reactions?

Atom Signup and view all the answers

What is the atomicity of Ozone?

3 Signup and view all the answers

Which element has the molecular formula P4?

Phosphorus Signup and view all the answers

Which of the following is true about elements?

Elements are made of only one kind of atoms. Signup and view all the answers

What is the proper atomicity for inert gases?

1 Signup and view all the answers

Which of the following combinations forms a molecule of a compound?

H2O Signup and view all the answers

What is the molecular formula and atomicity of Sulphur?

S8, 8 Signup and view all the answers

Which property distinguishes a compound from its constituent elements?

Compounds have a unique set of properties. Signup and view all the answers

What is true about the composition of a compound?

Elements are combined in a fixed proportion. Signup and view all the answers

Which of the following cannot separate the components of a compound?

Filtration Signup and view all the answers

Which of these compounds contains sulfur?

Hydrogen sulfide Signup and view all the answers

Which molecular formula represents a compound formed from three different elements?

H2SO4 Signup and view all the answers

Which statement about elements is correct?

Elements have unique properties. Signup and view all the answers

Study Notes

Elements

An element is a pure substance consisting of only one type of atom.
Elements are indivisible and cannot be broken down into simpler substances.
Common examples include oxygen, hydrogen, nitrogen, and sulfur.

Pure Substances

Defined as substances with uniform composition and the same particles.
Exhibit definite chemical and physical properties.
Examples include sugar, salt, and water.

Impure Substances

Comprised of two or more different kinds of particles.
Lack a definite composition and possess variable properties.
Common instances are milk, soil, and air.

Atom

The smallest indivisible unit of an element.
Atoms can engage in chemical reactions and may exist independently.

Structure of an Atom

Atoms feature a central nucleus containing protons (positively charged) and neutrons (neutral).
Electrons (negatively charged) orbit around the nucleus in designated paths known as orbits or shells.

Classification of Elements

Metals:
- Shiny appearance, hard solids, malleable and ductile.
- Good conductors of heat and electricity, with exceptions like sodium and mercury.
Non-metals:
- Dull, brittle, and non-malleable.
- Poor conductors, with graphite as an exception.
Metalloids:
- Exhibit mixed properties of metals and non-metals (e.g., Boron, Silicon, Germanium).
Noble Gases:
- Inert gases that do not react easily, such as Helium, Neon, Argon, Krypton, Xenon, and Radon.

Names and Symbols of Elements

Example: Iron is derived from the Latin "Ferrum" and is symbolized as Fe.
Tungsten comes from the German "Wolfram" and is symbolized as W.

Molecule

The smallest particle of a substance that retains all its properties.
Same elements form molecules of that element (e.g., H2, O2).
Different elements combine to form molecules of compounds (e.g., HCl, H2O).

Atomicity

Refers to the number of atoms in a molecule.
Metals and noble gases typically have an atomicity of one (monoatomic).
Examples of molecular formulas and atomicity:
- Hydrogen (H2) has atomicity 2, while Phosphorus (P4) has atomicity 4.

Characteristics of an Element

Composed solely of one kind of atom.
Cannot be decomposed into simpler substances through physical or chemical means.
Each element possesses unique properties.

Compounds

Comprised of two or more different elements combined chemically in a fixed proportion.
Examples include:
- Water (H2O)
- Ammonia (NH3)
- Carbon dioxide (CO2)

Characteristics of a Compound

Elements are chemically bonded in a specific ratio, such as two hydrogen atoms for each oxygen atom in water.
Compounds have distinct properties that differ from the individual properties of their constituent elements.
Elements in a compound cannot be separated by physical means, but can be separated chemically, as in the case of water through electrolysis.

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Description

Test your knowledge on elements, compounds, and mixtures with this quiz. Explore the definitions and examples of pure and impure substances. Understand the fundamental concepts of chemistry regarding various materials and their properties.