Biochemistry Atoms & Bonds Fundamentals Quiz

An atom is the smallest unit of matter that retains the chemical properties of an element. It consists of protons and neutrons in the nucleus, with electrons surrounding it. Living organisms, speed units, and rock formations are unrelated concepts. All matter, whether solid, liquid, or gas, is made up of atoms, making this concept foundational to chemistry and physics.

Isotopes are atoms of the same element, meaning they have the same number of protons. They differ in the number of neutrons, which changes their atomic mass but not their chemical behavior. This explains why isotopes of an element react similarly while having different stability or radioactive properties.

An ion forms when an atom gains or loses electrons. Losing electrons creates a positive ion, while gaining electrons creates a negative ion. The number of protons remains unchanged, so the charge difference comes only from electron imbalance, which is essential for electrical conductivity and chemical reactions.

Covalent bonds form when atoms share electrons to achieve stability. This usually occurs between non-metals with similar electronegativity values. Sharing electrons allows both atoms to fill their outer shells, making the molecule stable without forming charged particles, unlike ionic bonding.

Ionic bonds occur when one atom transfers electrons to another, forming oppositely charged ions. These ions attract each other due to electrostatic forces. This bond typically forms between metals and non-metals because of large electronegativity differences, leading to strong attractions.

Van der Waals forces are weak intermolecular attractions caused by temporary dipoles in molecules. They are much weaker than ionic or covalent bonds but are important in determining boiling points, molecular shapes, and interactions in large biological molecules.

A chemical reaction involves breaking old bonds and forming new ones, resulting in new substances. This differs from physical changes, which do not alter chemical identity. Chemical reactions follow conservation of mass and often involve energy changes.

Reactants are the starting substances in a chemical reaction. They undergo chemical changes to form products. Identifying reactants is essential for writing balanced chemical equations and understanding how reactions proceed.

Water is polar because it has a bent molecular shape and unequal sharing of electrons. Oxygen attracts electrons more strongly than hydrogen, creating partial charges. This polarity allows water to dissolve many substances and form hydrogen bonds.

A suspension is a heterogeneous mixture where solid particles are dispersed in a liquid but do not dissolve. Over time, these particles may settle. This distinguishes suspensions from solutions, where particles dissolve completely.

Acids release hydrogen ions when dissolved in water. This increases the concentration of H⁺ ions, lowering the pH. This behavior explains their sour taste and ability to react with bases in neutralization reactions.

Bases release hydroxide ions in solution, increasing pH levels. The OH⁻ ions reduce acidity and can neutralize acids. This property explains why bases feel slippery and are used in cleaning agents.

Acids have higher concentrations of hydrogen ions and are found below 7 on the pH scale. The pH scale is logarithmic, meaning each unit represents a tenfold change in acidity or basicity.

The Sun provides energy through sunlight, which plants convert into chemical energy using photosynthesis. This energy flows through food chains, supporting all living organisms either directly or indirectly.

Protons carry a positive charge and are located in the nucleus of an atom. Their number determines the element’s identity, making them fundamental to atomic structure and classification.

Oxidation is the loss of electrons during a chemical reaction. This process always occurs alongside reduction, forming a redox reaction essential in energy transfer and metabolism.

Saltwater is a homogeneous mixture because the salt dissolves completely and distributes evenly. The composition remains uniform throughout, unlike suspensions or colloids.

A chemical formula represents the elements in a compound and the number of atoms of each element. For example, H₂O shows two hydrogen atoms and one oxygen atom. It does not describe reactions or bonds but gives composition information essential for calculations.

The number of protons defines an element. Changing the proton count changes the element itself, while changing neutrons creates isotopes and changing electrons creates ions.

Ionic bonds form between metals and non-metals due to large electronegativity differences. This causes electron transfer and strong electrostatic attraction between ions.