Periodic Trends
Which direction does atomic radius generally change as you move down a group on the periodic table?
Increases
What is the atomic number of oxygen?
8
What is the chemical symbol for sodium?
Answer: Na
Ripping up a piece of paper is what type of change?
Answer: Physical
The outside layer of an atom that has a negative charge.
Answer: Electron
Explain why ionization energy generally increases as you move left to right across a period.
Ionization energy increases because nuclear charge increases while shielding stays similar.
Identify where electrons are located in an atom (name the region).
Answer: Electrons are located in the electron shell.
When oxygen gains two electrons, what is the resulting ion's charge?
Answer: -2
When a bike rusts, is it a chemical or physical change? Explain.
Answer: Chemical; rusting forms new compounds (iron oxide).
Define 'matter'
Answer: Anything that has mass and takes up space.
Predict which element (from the set Li, Be, B, C) has the smallest atomic radius and justify using periodic trends.
Answer: Carbon (C) has the smallest radius.
An atom has 11 protons and 12 neutrons. Give its element, atomic number, and mass number.
Answer: Sodium (Na), atomic number 11, mass 23.
How many neutrons are in potassium if its atomic number is 19 and its mass number is 39?
Answer: 20 neutrons.
Which of the following is a chemical change: melting ice, dissolving sugar, or copper penny turning green?
Answer: Copper penny turning green – new substance forms.
Match the particle: In the nucleus, has a positive charge.
Answer: Proton.
Describe how electronegativity changes across a period and down a group.
Answer: Electronegativity increases left to right and decreases down a group.
Explain how to determine the number of shells and valence electrons for sodium and chlorine.
Answer: Na → 3 shells, 1 valence; Cl → 3 shells, 7 valence.
Define the difference between an isotope and an ion. Give examples.
Answer: Isotope: same protons, different neutrons (C-12/C-14); Ion: charged (Na⁺/Cl⁻).
Describe what (g) means in a chemical equation and give an example.
Answer: (g) = gas; e.g., H₂(g) + Cl₂(g) → 2HCl(g).
Define homogeneous mixture, compound, and element, with examples.
Answer: Homogeneous: uniform (salt water); Compound: fixed ratio (NaCl); Element: one atom type (O₂).
Explain why Na+ is smaller than Na and Cl- is larger than Cl.
Answer: Na+ loses outer electrons; Cl- gains electrons increasing repulsion.
An atom has configuration 3s²3p⁵. Give element, protons, likely ion, and charge reason.
Answer: Chlorine (Cl), 17 protons, forms Cl⁻ by gaining one electron.
Given an atom with 19 protons and mass 39, calculate neutrons and electrons, ion form, and group.
Answer: Neutrons=20, electrons=19, K⁺ ion, Group 1 alkali metal.
Explain how to tell a physical from chemical change (2–3 sentences).
Answer: Look for color, gas, temperature, precipitate, reversibility.
Explain how table salt forms from Na and Cl including ion formation.
Answer: Na→Na⁺, Cl→Cl⁻, ionic bond forms NaCl.