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ATI TEAS: Chemistry Concepts

Importance ★★★★☆ · 18% (estimate)

Overview

This chapter covers the basics of matter and how it changes. You will learn the parts of an atom, how the periodic table is arranged, how atoms bond, the states of matter, how to balance a chemical equation, and how acids, bases, and solutions behave.

An atom has protons and neutrons in its nucleus and electrons around it. The atomic number is the number of protons, which decides which element it is, and the mass number is protons plus neutrons. Atoms of the same element with different numbers of neutrons are called isotopes. Ionic bonds form when electrons are transferred, usually between a metal and a nonmetal, while covalent bonds form when electrons are shared, usually between nonmetals.

A balanced chemical equation has the same number of each kind of atom on both sides, because matter is not created or destroyed. The pH scale runs from 0 to 14: below 7 is acidic, 7 is neutral, and above 7 is basic. In a solution, the solute is the substance being dissolved and the solvent is the substance doing the dissolving.

Key concepts

  • Parts of an atom

    Protons (positive) and neutrons (no charge) sit in the nucleus; electrons (negative) move around it. A neutral atom has equal numbers of protons and electrons.

    Memory tipProtons positive, neutrons neutral, electrons negative.

  • Atomic number, mass number

    Atomic number = number of protons and identifies the element. Mass number = protons + neutrons. Neutrons = mass number - atomic number.

    Memory tipChange the protons and you change the element.

  • Isotope

    Atoms of the same element (same number of protons) with different numbers of neutrons, so they have different mass numbers.

    Memory tipIsotopes: same protons, different neutrons.

  • Ionic vs. covalent bond

    An ionic bond forms when one atom gives electrons to another, usually metal to nonmetal. A covalent bond forms when atoms share electrons, usually between nonmetals.

    Memory tipIonic = give and take; covalent = share.

  • Balancing equations

    Adjusting the coefficients in front of formulas so each element has the same number of atoms on both sides. Example: 2H2 + O2 -> 2H2O.

    Memory tipChange coefficients, never subscripts.

  • pH scale

    A 0 to 14 scale of how acidic or basic a solution is. Below 7 is acidic, 7 is neutral (pure water), and above 7 is basic.

    Memory tipLower pH = more acidic.

  • Solute and solvent

    In a solution, the solute is the substance dissolved (such as salt) and the solvent is what it dissolves in (such as water).

    Memory tipThe solvent does the dissolving.

Often tested

  • Elements in the same column (group) of the periodic table have similar chemical properties.
  • Melting, freezing, and boiling are physical changes; burning and rusting are chemical changes.
  • In a balanced equation, total mass of reactants equals total mass of products.
  • Acids release hydrogen ions (H+) in water; bases release hydroxide ions (OH-) or accept H+.

Easy to confuse: Ionic vs. covalent bonds

FeatureIonicCovalent
ElectronsTransferredShared
Usual elementsMetal + nonmetalNonmetal + nonmetal
ExampleTable salt (NaCl)Water (H2O)

3 sample questions

Verified practice questions from this unit.

Practice questionReviewedScience › Chemistry★★★★☆

Question 1. An oxygen atom has an atomic number of 8. How many protons does it have?

  1. ① 8
  2. ② 16
  3. ③ 4
  4. ④ 2
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ① 8

Key point: Atomic number = number of protons

The atomic number is the number of protons in an atom. Every oxygen atom has 8 protons. (A neutral atom also has the same number of electrons, 8.)

Wrong choices

  • 16: 16 is the usual mass number of oxygen (protons + neutrons).
  • 4: This is half the atomic number.
  • 2: This has no connection to the atomic number.
Practice questionReviewedScience › Chemistry★★★★☆

Question 2. Which pH value describes an acidic solution?

  1. ① pH 7
  2. ② pH 9
  3. ③ pH 3
  4. ④ pH 12
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ③ pH 3

Key point: pH < 7 acidic, 7 neutral, > 7 basic

The pH scale runs from 0 to 14. Below 7 is acidic, 7 is neutral, and above 7 is basic. A pH of 3 is acidic.

Wrong choices

  • pH 7: pH 7 is neutral, like pure water.
  • pH 9: A pH above 7 is basic.
  • pH 12: pH 12 is strongly basic.
Practice questionReviewedScience › Chemistry★★★★☆

Question 3. Which particle in an atom has a negative charge?

  1. ① Proton
  2. ② Neutron
  3. ③ Electron
  4. ④ Nucleus
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ③ Electron

Key point: Protons +, neutrons 0, electrons −

Atoms have three main particles: protons (positive) and neutrons (no charge) in the nucleus, and electrons (negative) moving around the nucleus.

Wrong choices

  • Proton: Protons have a positive charge.
  • Neutron: Neutrons have no charge.
  • Nucleus: The nucleus is the atom's center and has an overall positive charge from its protons.
Practice 5 questions from this unit →

AI-written · Verified · Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.