Structure of Atoms, Periodic Table & Chemical Bonding

Question 1

Describe the composition of an atomic nucleus.

Answer 1

An atomic nucleus is composed of protons, which have a positive charge (+1), and neutrons, which have no charge (0).

Question 2

Define isotopes and their significance.

Answer 2

Isotopes are atoms of the same element that have different numbers of neutrons, resulting in different mass numbers. They are significant in various applications, including radiometric dating and medical diagnostics.

Question 3

How do radioactive isotopes decay?

Answer 3

Radioactive isotopes undergo spontaneous decay of the atomic nucleus, losing energy and particles. For example, one neutron can decay into a proton, transforming carbon-14 into nitrogen-14.

Question 4

Explain the concept of half-life in radioactive isotopes.

Answer 4

Half-life is the time it takes for 50% of a parent isotope to decay. This rate is fixed for each isotope and is used in various scientific applications.

Question 5

What are the applications of radioactive isotopes in medicine?

Answer 5

Radioactive isotopes are used as diagnostic tools in medicine, such as in Positron Emission Tomography (PET) radiotracers, which help visualize metabolic activity in tissues.

Question 6

Describe the structure of atoms in terms of electrons.

Answer 6

Atoms have electrons, which are negatively charged (-1), surrounding the nucleus. The number of electrons typically equals the number of protons in a neutral atom.

Question 7

How are elements distinguished from one another?

Answer 7

Elements are distinguished by the number of protons in their atomic nuclei, which is known as the atomic number.

Question 8

What is the significance of the periodic table in chemistry?

Answer 8

The periodic table organizes elements based on their atomic number and properties, providing a framework for understanding chemical behavior and relationships.

Question 9

Explain the difference between intramolecular and intermolecular bonding.

Answer 9

Intramolecular bonding refers to the forces that hold atoms together within a molecule (e.g., ionic, covalent, metallic bonds), while intermolecular interactions are forces between molecules (e.g., van der Waals forces, hydrogen bonds).

Question 10

What role do van der Waals forces play in molecular interactions?

Answer 10

Van der Waals forces are weak intermolecular interactions that occur between molecules, influencing properties such as boiling and melting points.

Question 11

Describe the significance of hydrogen bonds in biological systems.

Answer 11

Hydrogen bonds are crucial in biological systems as they help stabilize the structures of proteins and nucleic acids, such as DNA.

Question 12

How does the atomic mass relate to the mass number of an element?

Answer 12

The atomic mass of an element is approximately equal to its mass number, which is the sum of protons and neutrons in the nucleus.

Question 13

What is the atomic mass of sodium (Na)?

Answer 13

The standard atomic mass of sodium (Na) is approximately 22.990.

Question 14

Define the term ‘element’ in chemistry.

Answer 14

An element is a pure substance that cannot be broken down into simpler substances by chemical reactions and is defined by its unique number of protons.

Question 15

How do unstable isotopes differ from stable isotopes?

Answer 15

Unstable isotopes undergo radioactive decay, losing energy and particles over time, while stable isotopes do not change and remain constant.

Question 16

What is the role of carbon-14 in scientific studies?

Answer 16

Carbon-14 is used in radiometric dating to determine the age of fossils and archaeological artifacts due to its radioactive properties.

Question 17

Describe the relationship between atomic number and element identity.

Answer 17

The atomic number, which is the number of protons in an atom’s nucleus, uniquely identifies an element and determines its position in the periodic table.

Question 18

Describe the arrangement of electrons in an atom.

Answer 18

Electrons localize around the atomic nucleus in different electron shells, also known as energy levels.

Question 19

Define the term ‘subshell’ in the context of electron configuration.

Answer 19

Subshells are divisions of energy levels that contain orbitals, which can be s, p, d, or f.

Question 20

How many electrons can a single orbital contain?

Answer 20

Each orbital can contain up to 2 electrons, which spin in opposite directions to minimize repulsion.

Question 21

What shapes are associated with the different types of orbitals?

Answer 21

s orbitals are spherical, p orbitals are dumbbell-shaped, d orbitals resemble a four-leaf clover, and f orbitals have a tetrahedral shape.

Question 22

Explain the concept of electron configuration using Sodium as an example.

Answer 22

Sodium (11 electrons) has the electron configuration 1s2, 2s2, 2p6, 3s1.

Question 23

What is the electron configuration for Copper?

Answer 23

Copper (29 electrons) has the electron configuration 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1.

Question 24

Differentiate between cations and anions.

Answer 24

Cations are positive ions formed when metal atoms lose electrons, while anions are negative ions formed when non-metal atoms gain electrons.

Question 25

How are elements organized in the periodic table?

Answer 25

Elements are arranged in order of increasing atomic number, organized into groups (columns) and periods (rows).

Question 26

What is electronegativity and how does it vary in the periodic table?

Answer 26

Electronegativity is the power of an atom to attract a pair of electrons in a chemical bond; it increases across a period and decreases down a group.

Question 27

Describe the characteristics of transition metals.

Answer 27

Transition metals are elements in the d block of the periodic table, known for their ability to form colored compounds and having unique properties.

Question 28

What is the significance of the principal quantum number in electron configuration?

Answer 28

The principal quantum number indicates the energy level of an electron in an atom, determining its distance from the nucleus.

Question 29

How do the number of electrons relate to the number of shells in an atom?

Answer 29

The number of electrons determines how many shells are filled; each shell can hold a specific maximum number of electrons.

Question 30

What is the role of ATP in relation to ions in cells?

Answer 30

ATP helps balance the positive charge of ions like Na+ and Ca2+ in cells.

Question 31

Explain the concept of orbitals in three-dimensional space.

Answer 31

Orbitals are three-dimensional spaces around the nucleus where electrons are likely to be found.

Question 32

How does the arrangement of elements in the periodic table reflect their chemical properties?

Answer 32

Elements with similar chemical properties are grouped together in columns, while rows indicate the filling of energy levels.

Question 33

Describe ionic bonds.

Answer 33

Ionic bonds are formed through the electrostatic attraction between two oppositely charged ions, typically involving the transfer of electrons from metal atoms (which lose electrons) to non-metal atoms (which gain electrons).

Question 34

Define covalent bonds.

Answer 34

Covalent bonds are formed when one or more pairs of valence electrons are shared between atoms, commonly occurring between non-metal elements.

Question 35

How do ionic compounds form?

Answer 35

Ionic compounds form when metal atoms lose electrons to become positively charged ions, while non-metal atoms gain those electrons to become negatively charged ions, resulting in the formation of salts.

Question 36

What are the characteristics of metallic bonds?

Answer 36

Metallic bonds are characterized by the electrostatic attraction between delocalised electrons and metal ions, allowing metals to conduct electricity and heat due to the mobility of these electrons.

Question 37

Explain the structure of salts.

Answer 37

Salts are organized in three-dimensional structures known as ionic lattices or crystals, which exhibit a cubic arrangement.

Question 38

How do covalent bonds differ in polarity?

Answer 38

Covalent bonds can be non-polar, where atoms have equal electronegativity, or polar, where atoms have different electronegativities, resulting in a partial charge.

Question 39

What is the significance of valence electrons in chemical bonding?

Answer 39

Valence electrons are crucial in determining the chemical behavior and reactivity of atoms, as they are involved in the formation of chemical bonds.

Question 40

Describe the formation of a water molecule.

Answer 40

A water molecule (H2O) is formed when two hydrogen atoms each share one pair of electrons with an oxygen atom, resulting in two single covalent bonds.

Question 41

How do metallic bonds contribute to the properties of metals?

Answer 41

Metallic bonds allow for the presence of delocalised electrons, which can move freely through the metal, enabling metals to conduct electricity and heat effectively.

Question 42

What is a non-polar covalent bond?

Answer 42

A non-polar covalent bond occurs between atoms with equal electronegativity, resulting in an equal sharing of electrons.

Question 43

What is a polar covalent bond?

Answer 43

A polar covalent bond occurs between atoms with different electronegativities, leading to an unequal sharing of electrons and the creation of a partial charge.

Question 44

How do covalent bonds relate to molecules?

Answer 44

Atoms linked by covalent bonds are referred to as molecules, which can consist of two or more atoms sharing electrons.

Question 45

Explain the concept of delocalised electrons in metallic bonds.

Answer 45

Delocalised electrons in metallic bonds are valence electrons that are not bound to any specific atom and can move freely throughout the metal structure, contributing to conductivity.

Question 46

What happens to noble gases in terms of bonding?

Answer 46

Noble gases have full outer electron shells, which means they do not form bonds and are generally unreactive.

Question 47

Describe the electron configuration of a sodium atom.

Answer 47

The electron configuration of a sodium atom is 1s2, 2s2, 2p6, 3s1, indicating it has one valence electron in its outermost shell.

Question 48

How many covalent bonds does an oxygen molecule (O2) have?

Answer 48

An oxygen molecule (O2) has a double bond, formed by two pairs of shared electrons between the two oxygen atoms.

Question 49

What is the role of electronegativity in polar covalent bonds?

Answer 49

Electronegativity determines the strength of an atom’s attraction for shared electrons; in polar covalent bonds, the atom with higher electronegativity attracts the shared electrons more strongly.

Question 50

Describe London dispersion forces.

Answer 50

London dispersion forces are the weakest intermolecular forces, also known as temporary dipole-induced dipole forces, that form between non-polar molecules due to transitory uneven electron distribution.

Question 51

Explain dipole-dipole forces.

Answer 51

Dipole-dipole forces are permanent intermolecular forces that occur between polar molecules, where opposite charged poles attract each other, and they are stronger than London dispersion forces but only about 1% of a covalent bond’s strength.

Question 52

How do gecko lizards utilize van der Waals forces?

Answer 52

Gecko lizards can adhere to walls thanks to van der Waals forces that form between tiny hairy structures on their feet and the surface, involving hundreds of thousands of these forces.

Question 53

Define hydrogen bonds and their significance.

Answer 53

Hydrogen bonds are the strongest form of intermolecular force, involving hydrogen bound to oxygen, nitrogen, or fluorine, resulting in highly polar molecules with permanent dipoles.

Question 54

What role do weak interactions play in macromolecules?

Answer 54

Weak interactions such as van der Waals forces, hydrogen bonds, and ionic bonds are fundamental in forming the 3D structure of macromolecules like proteins and nucleic acids.

Question 55

What is the significance of electronegativity in hydrogen bonds?

Answer 55

Electronegativity creates a large difference between atoms in hydrogen bonds, leading to highly polar molecules and strong attractions between hydrogen and electron pairs of other molecules.

Question 56

How do weak interactions contribute to biological processes?

Answer 56

Weak interactions are crucial for the stability and functionality of biological macromolecules, influencing their 3D structures and interactions.

Question 57

Define molarity in the context of chemistry.

Answer 57

Molarity is a measure of the concentration of a solute in a solution, expressed as the number of moles of solute per liter of solution.