Chemistry, Atomic Structure, and Radioactivity

Comprehensive vocabulary flashcards covering atomic structure, periodic trends, Bohr models, ionic bonding, crystal lattices, chemical reactions, spreadsheet data management, radiation decay types, and half-life analysis.

Atom

The smallest unit of an element that retains the chemical properties of that element, serving as the basic building block of all matter.

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Neutron

A neutrally charged subatomic particle located in the nucleus of an atom.

Electron

A negatively charged subatomic particle that orbits the nucleus in specific energy levels or shells.

Nucleus

The dense, central part of an atom containing protons and neutrons.

Atomic Number

The number of protons in an atom's nucleus, which uniquely identifies the element.

Atomic Mass

The total number of protons and neutrons in an atom's nucleus (also known as the mass number).

Periodic Table

A chart that organizes all known chemical elements in order of increasing atomic number.

Period

A horizontal row on the periodic table, where each period represents a new electron shell.

Group

A vertical column on the periodic table containing elements that share similar chemical properties because they have the same number of valence electrons.

Bohr Model

A diagram that shows the arrangement of an atom's protons, neutrons, and electrons, with the nucleus at the center and electrons orbiting in shells.

Electron Shell

An energy level where electrons orbit the nucleus; holds a maximum of $2$ electrons in shell 1, $8$ electrons in shell 2, and $8$ electrons in shell 3 (for the first 20 elements).

Octet Rule

The tendency of atoms to achieve stability by having a full outer electron shell, which is usually eight electrons.

Valence Electrons

The electrons situated in the outermost shell of an atom that participate in chemical bonding.

Ion

A charged atom formed when a neutral atom gains or loses electrons.

Cation

A positively charged ion formed when an atom loses one or more negative electrons; typically formed by metal atoms with $1$, $2$, or $3$ valence electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons to attain a full octet; typically formed by nonmetal atoms with $5$, $6$, or $7$ valence electrons.

Valence Shell

The outermost electron shell of an atom.

Lewis Dot Diagram

A simplified model that shows an element's symbol (representing the nucleus and inner shells) surrounded by dots representing its valence electrons.

Single Displacement Reaction

A chemical reaction where one element displaces another in a compound, exemplified by $Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)$.

Magnesium Chloride

The ionic compound ($MgCl_2$) formed when one $Mg^{2+}$ ion balances with two $Cl^-$ ions following electron transfer.

Hydrogen Gas

The gaseous byproduct ($H_2$) released during the single displacement reaction between magnesium metal and hydrochloric acid.

Ionic Bond

A strong electrostatic attraction between a positively charged ion (cation) and a negatively charged ion (anion), formed when a metal transfers valence electrons to a nonmetal.

Ionic Compound

A neutral compound composed of cations and anions held together by ionic bonds such that the total positive charge equals the total negative charge.

Criss-Cross Method

A method for determining the formula of an ionic compound by crossing the numerical values of the ionic charges to become the subscripts of the opposite ions, then reducing to the lowest whole-number ratio.

Coefficient

A whole number placed in front of a chemical formula in an equation to balance the number of atoms of each element without changing subscripts.

Polyatomic Ion

A group of covalently bonded atoms that carries an overall net charge (such as $SO_4^{2-}$ or $NO_3^-$) and can be treated as a single unit when balancing chemical equations.

Electrostatic Attraction

The force of attraction between opposite electric charges that binds cations and anions together in multiple directions.

Crystal Lattice

A highly ordered, repeating three-dimensional structure formed by ions in an ionic compound that maximizes attraction between opposite charges while minimizing repulsion.

Accuracy

A measure of how close experimental measurements are to the true or target value (correctness).

Precision

A measure of how close experimental measurements are to each other (consistency).

Measurement Uncertainty

The margin of error recorded along with units in the table column heading (e.g., $\text{Mass of Beaker with Water / g } (\pm 0.01\,\text{g})$), rather than inside data cells.

Raw Data

Quantitative observations recorded directly from laboratory instruments to the correct number of significant figures prior to any mathematical manipulation or subtraction.

AVERAGE Function

A spreadsheet formula (e.g., =AVERAGE(B2:D2)) used to automatically calculate the mean value of a specified cell range.

Radioactivity

The spontaneous process by which an unstable atomic nucleus loses energy by emitting radiation and particles (radioactive decay).

Radioisotope

An atom with an unstable nucleus caused by an imbalance in the forces holding protons and neutrons together.

Alpha Decay

Radioactive decay in heavy nuclei ($Z > 83$) that releases an alpha particle, decreasing atomic mass by $4$ and atomic number by $2$.

Alpha Particle

A particle emitted during alpha decay composed of $2$ protons and $2$ neutrons (identical to a Helium nucleus, ${^4_2\text{He}}$), which can be stopped by a sheet of paper or human skin.

Beta Decay

Radioactive decay occurring in neutron-rich nuclei where a neutron converts into a proton and an electron; results in no mass change and an atomic number increase of $1$.

Beta Particle

A high-speed, high-energy electron (${^0_{-1}\text{e}}$) emitted from the nucleus during beta decay, which can be stopped by an aluminum sheet or wood.

Gamma Decay

The release of pure excess energy as high-energy electromagnetic waves from an excited nucleus to return to ground state, producing no change in atomic mass or atomic number.

Gamma Ray

Pure electromagnetic energy with the highest penetrating power of radioactive emissions, requiring thick lead or concrete to stop.

Half-Life

The fixed amount of time ($t_{1/2}$) required for half of the radioactive atoms in a sample to decay.

Activity

The rate of radioactive decay of a sample, commonly measured in counts per second or counts per minute.

Decay Graph

A plot of radioactive activity on the y-axis against time on the x-axis, forming a characteristic exponential curve used to determine half-life.