Science Test

What is the structure of an atom?

An atom has a central nucleus containing protons and neutrons, with electrons moving around the nucleus in electron shells.

What are the three subatomic particles in an atom?

Protons, neutrons, and electrons.

What are the properties of protons?

Protons have a positive charge (+1), are located in the nucleus, and have a relative mass of 1.

What are the properties of neutrons?

Neutrons have no charge (0), are located in the nucleus, and have a relative mass of 1.

What are the properties of electrons?

Electrons have a negative charge (−1), move around the nucleus in shells, and have a very small mass (~1/1836 of a proton).

What is an atomic symbol?

A shorthand way of representing an element showing its chemical symbol, mass number, and atomic number.

What does the atomic number represent?

The number of protons in the nucleus of an atom.

What does the mass number represent?

The total number of protons and neutrons in the nucleus.

How does the number of protons determine an element's atomic number?

The atomic number is equal to the number of protons in the nucleus and identifies the element.

Why are atoms charge-neutral?

Because the number of negatively charged electrons equals the number of positively charged protons.

What is electron configuration?

The arrangement of electrons in the shells around the nucleus of an atom.

How do you calculate electron configuration?

Fill electron shells from the inside outward (first shell holds 2 electrons, second 8, third 8 for basic models).

What is the difference between an atom and an ion?

An atom is neutral, while an ion is an atom that has gained or lost electrons and therefore has a charge.

What is an ion?

A charged atom formed when electrons are gained or lost.

What is a cation?

A positively charged ion formed when an atom loses electrons.

What is an anion?

A negatively charged ion formed when an atom gains electrons.

How are ions formed from neutral atoms?

By gaining electrons (forming anions) or losing electrons (forming cations).

How do charged particles interact?

Opposite charges attract and like charges repel.

What is a chemical formula?

A combination of element symbols showing the types and numbers of atoms in a compound.

How do you write the chemical formula of an ionic compound?

By balancing the charges of the positive and negative ions so the overall compound is neutral.

How can chemical formulae help identify ionic compounds?

Ionic compounds usually consist of a metal ion and a non-metal ion combined in a ratio that balances charge.

How does the number of neutrons affect the mass number?

The mass number equals the number of protons plus neutrons, so changing neutrons changes the mass number.

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

How does mass number relate to isotopes?

Isotopes have different mass numbers because they contain different numbers of neutrons.

What are atomic symbols for common elements?

Examples include H (hydrogen), O (oxygen), C (carbon), Na (sodium), Cl (chlorine), and Fe (iron).

What are reactants in a chemical reaction?

The substances present at the start of a chemical reaction.

What are products in a chemical reaction?

The new substances formed in a chemical reaction.

What is a word equation?

A chemical reaction written using the names of substances (e.g., hydrogen + oxygen → water).

What is a formula equation?

A chemical reaction written using chemical formulas.

What is an unbalanced chemical equation?

A formula equation where the number of atoms of each element is not equal on both sides.

What is the law of conservation of mass?

Mass cannot be created or destroyed in a chemical reaction; the total mass of reactants equals the total mass of products.

How do you balance a chemical equation?

By adjusting coefficients so the number of each type of atom is the same on both sides.

What is nuclear decay?

The process where an unstable atomic nucleus loses energy by emitting radiation.

What are nuclear reactions?

Changes that occur in the nucleus of an atom, such as radioactive decay.

What are radioisotopes?

Isotopes with unstable nuclei that undergo radioactive decay.

How are radioisotopes different from stable isotopes?

Radioisotopes are unstable and emit radiation, while stable isotopes do not decay.

What are the three types of nuclear decay?

Alpha decay, beta decay, and gamma decay.

What is alpha decay?

The emission of an alpha particle (2 protons and 2 neutrons) from the nucleus.

What is beta decay?

The emission of a beta particle (a high-energy electron) from the nucleus.

What is gamma decay?

The release of high-energy electromagnetic radiation from the nucleus.

What is half-life?

The time it takes for half of the radioactive nuclei in a sample to decay.

How can half-life be interpreted from a graph?

By identifying the time taken for the amount of radioactive material to decrease to half its original value.