Smallest Unit Measure Practice Quiz

An atom is the basic unit of matter that cannot be split by chemical means. Molecules and compounds are formed by combinations of atoms.

The proton carries a positive charge and is located in the nucleus of an atom. Other subatomic particles either have a negative charge or are neutral.

An element is defined as a pure substance made of atoms that all have the same number of protons. Mixtures or compounds contain more than one type of atom.

The atom is considered the fundamental building block of an element. Other options represent structures that are composed of atoms.

Electrons carry a negative charge and orbit the nucleus. Protons are positive and neutrons are neutral, while quarks are constituents of protons and neutrons.

The atomic number is defined by the number of protons in the nucleus. It uniquely identifies each element on the periodic table.

An ion is formed when an atom gains or loses electrons, resulting in a net charge. This change disrupts the balance between protons and electrons.

Molecules form when two or more atoms share or transfer electrons to achieve a stable arrangement. They are typically neutral and can be made up of identical or different atoms.

The nucleus of an atom contains both protons and neutrons, which account for most of its mass. Electrons are found in orbitals surrounding the nucleus.

The mass number is the total count of protons and neutrons, which closely approximates the atomic mass. Electrons have a negligible effect on the mass, making the two values nearly identical.

Elements are arranged in the periodic table in order of increasing atomic number. This organization helps in understanding recurring chemical properties and trends.

The Bohr model depicts electrons moving in fixed circular orbits around the nucleus. Although this model has been refined by quantum mechanics, it laid the groundwork for understanding atomic structure.

Isotopes are variants of a particular element that have the same number of protons but differ in the number of neutrons. This variance affects their atomic mass while leaving chemical properties largely unchanged.

The atomic nucleus is positively charged due to the presence of protons. Neutrons, which also reside in the nucleus, do not contribute to the charge as they are neutral.

Covalent bonds form when atoms share electron pairs, allowing them to achieve greater stability. This type of bonding is distinct from ionic bonds, where electrons are transferred rather than shared.

The quantum mechanical model describes electrons as existing in electron clouds where their positions are given in terms of probability. This differs from classical models which depicted electrons in fixed orbits.

Atomic theory supports the law of conservation of matter by asserting that atoms remain intact during chemical reactions. They are merely rearranged to form new compounds, rather than being created or destroyed.

The size of an atom is largely determined by the number of electron shells it has; more shells mean a larger atomic radius. While nuclear charge plays a role, the addition of electron shells is the dominant factor in atomic size.

An element's chemical reactivity is primarily influenced by the electrons in its outermost shell. These electrons dictate how atoms interact and form bonds with other elements.

Electron diffraction experiments reveal patterns that indicate electrons exist in regions of probability known as electron clouds. This evidence supports the quantum mechanical model over the classical fixed orbit model.