Chemistry Chapter 2.1: Chemical Elements

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Questions and Answers

What happens to sodium when it forms an ionic bond?

It shares its electron.

It gains an electron.

It loses an electron. (correct)

It becomes negatively charged.

What is the resulting charge of a sodium ion after losing an electron?

-1

+1 (correct)

In covalent bonding, how does a double bond differ from a single bond?

A double bond is weaker than a single bond.

A double bond involves the sharing of two pairs of electrons. (correct)

A single bond involves the sharing of one pair of electrons.

A double bond involves the sharing of three pairs of electrons.

What characterizes a polar covalent bond?

One atom attracts electrons more than the other. Signup and view all the answers

Which of the following describes electronegativity?

The ability of an atom to attract electrons. Signup and view all the answers

What is sodium chloride (NaCl) primarily held together by?

Ionic bonds. Signup and view all the answers

Which compound represents a non-polar covalent bond?

H2 Signup and view all the answers

What occurs when chlorine gains an electron?

Chlorine becomes negatively charged. Signup and view all the answers

Which elements make up approximately 95% of the body weight of organisms?

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur Signup and view all the answers

What determines the atomic number of an element?

The number of protons in the nucleus Signup and view all the answers

What is the mass number of an atom if it contains 12 protons and 14 neutrons?

26 Signup and view all the answers

In which part of an atom are protons and neutrons located?

In the nucleus Signup and view all the answers

Which of the following statements about mass and weight is true?

Mass is constant, while weight can change depending on gravity Signup and view all the answers

Which atomic symbol represents the configuration of a helium atom?

4He Signup and view all the answers

What is considered negligible in terms of atomic mass?

Electrons Signup and view all the answers

Which of the following states of matter does not include gases?

Both A and B Signup and view all the answers

What does the atomic number represent in an atom?

The total number of protons and electrons in the atom Signup and view all the answers

How can you determine the number of neutrons in an atom?

Subtract the atomic number from the atomic mass Signup and view all the answers

Which statement accurately describes isotopes?

Isotopes have the same number of electrons and protons but different masses. Signup and view all the answers

What characterizes noble gases in the periodic table?

They are inert and rarely react with other atoms. Signup and view all the answers

Which of the following correctly describes a compound?

It is formed when two or more elements bond together. Signup and view all the answers

What type of bond is formed through the electrostatic attraction between oppositely charged ions?

Ionic bond Signup and view all the answers

What is the smallest part of a compound commonly referred to in biology?

Molecule Signup and view all the answers

Which formula represents a molecule containing atoms of hydrogen and oxygen?

H2O Signup and view all the answers

What is the angle between the covalent bonds in a water molecule?

104.5° Signup and view all the answers

Which property of water is primarily attributed to hydrogen bonding?

High boiling point Signup and view all the answers

What would happen to water's state at higher temperatures without hydrogen bonding?

It would boil at lower temperatures Signup and view all the answers

Why does water have a high heat capacity?

Hydrogen bonds need to be broken before temperature changes Signup and view all the answers

What role does the shape of the water molecule play in living organisms?

Enabling hydrogen bonding Signup and view all the answers

What is the state of water at 0°C under normal atmospheric conditions?

Liquid Signup and view all the answers

What is the effect of hydrogen bonding on water's temperature change?

Water warms up slowly Signup and view all the answers

What is the significance of identifying signs of water on other planets?

It suggests a potential for life Signup and view all the answers

What mechanism does an animal's body use to cool itself when sweating?

Evaporation of sweat absorbs heat. Signup and view all the answers

What property of water allows ionic salts to dissociate in solution?

Polarity of water molecules. Signup and view all the answers

Which type of molecules cannot attract water and are therefore hydrophobic?

Non-polar molecules. Signup and view all the answers

What causes water to exist as a liquid under ordinary conditions?

Hydrogen bonding between molecules. Signup and view all the answers

How does cohesion contribute to the transport of water in plants?

It enables water molecules to remain intact in the xylem. Signup and view all the answers

What is capillary action primarily caused by?

Stronger adhesive forces than cohesive forces. Signup and view all the answers

What role does adhesion play in the movement of water in narrow tubes?

It pulls the water molecules toward the tube walls. Signup and view all the answers

Why is water considered a universal solvent?

It can dissolve a wide range of substances due to its polarity. Signup and view all the answers

Study Notes

2.1 Chemical Elements

Matter exists as a solid, liquid, or gas and is made up of elements, which cannot be broken down into simpler substances.
There are 92 known elements, and six are crucial for life: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS).
An atom is the smallest unit of an element that still retains the properties of that element.
Atoms are composed of three subatomic particles: protons, neutrons, and electrons.
Protons are positively charged and reside in the nucleus of an atom.
Neutrons have no charge and reside in the atom's nucleus.
Electrons are negatively charged and orbit the nucleus.
The atomic number represents the number of protons in an atom's nucleus.
The mass number is the sum of protons and neutrons in an atom's nucleus.
The periodic table organizes elements based on their chemical and physical properties.
Elements in the same group (vertical column) share similar bonding characteristics.
Isotopes of the same element have the same number of protons but differ in the number of neutrons.
Some isotopes, like carbon-14, are unstable and radioactive.

2.2 Compounds and Molecules

A compound is formed when two or more elements bond together.
A molecule is the smallest unit of a compound.
Water (H₂O) is a molecule composed of hydrogen and oxygen atoms.
Molecules are often referred to as compounds in biological contexts.

2.2 Chemical Bonds

Ionic Bonding:
- Forms from electrostatic attraction between oppositely charged ions.
- Example: Table salt (NaCl), formed by the attraction between sodium (Na⁺) and chloride (Cl⁻) ions.
- Sodium loses an electron to become a positively charged ion (Na⁺), while chlorine gains an electron to become a negatively charged ion (Cl⁻).
Covalent Bonding:
- Atoms share electrons to complete their outer shell (octet).
- Example: Hydrogen gas (H₂), where two hydrogen atoms share their electrons.
- A double covalent bond involves two pairs of shared electrons, as in oxygen gas (O₂).
Polar and Non-polar Covalent Bonds:
- In a non-polar covalent bond, electrons are shared equally between atoms.
- In a polar covalent bond, one atom is more electronegative (attracts electrons more strongly) than the other.
- Example: Water (H₂O), where oxygen is more electronegative than hydrogen, creating a polar covalent bond.

2.3 Chemistry of Water

Water makes up 70-90% of all living cells.
The shape of the water molecule is essential for its properties and functions.
Water is a polar molecule, with a bent shape due to the lone pairs of electrons on oxygen.
Hydrogen bonding occurs between water molecules due to the attraction between a partially positive hydrogen atom on one molecule and a partially negative oxygen atom on another.

Properties of Water

High Heat Capacity & Heat of Evaporation:
- Due to hydrogen bonds, water absorbs significant heat without a large change in temperature.
- This property helps regulate body temperature in organisms.
Excellent Solvent:
- Water's polarity allows it to dissolve many substances, making it a universal solvent.
- Hydrophilic molecules can dissolve in water, while hydrophobic molecules cannot.
Cohesive & Adhesive Nature:
- Cohesion refers to the ability of water molecules to stick together due to hydrogen bonding.
- Adhesion refers to the ability of water molecules to stick to other polar surfaces.
- These properties facilitate water transport in organisms, for example, in blood vessels and plant vascular systems.
Capillary Action:
- A combination of adhesion and cohesion enables water to move up narrow tubes against gravity, known as capillary action.
- This property plays a role in water transport in plants.

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Explore the fundamentals of chemical elements in this quiz. Learn about the main building blocks of matter, the structure of atoms, and the organizing principles of the periodic table. Test your knowledge on crucial life elements and their properties.