Periodic Table Basics
What does an element’s atomic number tell you?
The number of protons in the nucleus
What do all elements in the same group (column) of the periodic table have in common?
The same number of valence electrons
What is electronegativity?
The ability of an atom to attract an electron in a bond
What is the focus of nuclear chemistry?
The study of changes that occur in the nucleus of atoms
What do valence electrons determine about an atom?
How (or if) the atom will react chemically
What two subatomic particles are added together to get the mass number?
Protons and neutrons
What are the elements in Group 1 called, and what is one property they share?
Alkali metals; they are soft, shiny, and very reactive
What is ionization energy?
The energy required to remove an electron from an atom
What is radioactive decay?
The process where an unstable nucleus releases particles or energy to become more stable
State the octet rule.
Atoms tend to gain, lose, or share electrons to achieve 8 valence electrons in their outer shell
Why do isotopes of the same element have different mass numbers?
Because they have different numbers of neutrons
What type of element has properties between metals and nonmetals?
Metalloids or semiconductors
How does atomic radius change across a period (left to right)?
It decreases
Name the three main types of nuclear radiation.
Alpha, beta, and gamma radiation
Why are atoms with 1 or 7 valence electrons the most reactive?
They are only one electron away from having a full valence shell
If an atom has 11 protons, 12 neutrons, and 11 electrons, identify the element and its mass number.
Sodium (Na), mass number = 23
Why are noble gases considered inert?
Their outer electron shells are full, so they do not readily form bonds
Why do atomic radii decrease as you move from left to right across a period?
Because the number of protons increases, pulling electrons closer to the nucleus without adding a new energy level.
What is the difference between nuclear fission and fusion?
Fission splits a large atom into smaller ones; fusion combines small atoms into one larger atom
Rank sodium, magnesium, and aluminum by reactivity, and explain why.
Sodium > Magnesium > Aluminum because it has only one valence electron that is easiest to lose
Why do elements in the same group have similar chemical properties even though their atomic numbers are different?
Because they have the same number of valence electrons, which causes them to form bonds and react in similar ways despite having different numbers of energy levels.
Compare the reactivity of sodium and magnesium. Which is more reactive and why?
Sodium, because it has one valence electron that is easier to lose than magnesium’s two
Why does knowing the trend for electronegativity allow you to predict the trend for ionization energy?
Because both properties increase for the same reason — atoms with stronger attraction for electrons (higher electronegativity) also hold on more tightly to their own electrons, requiring more energy to remove one (higher ionization energy).
Explain why fission produces more radioactive waste than fusion.
Fission creates unstable daughter nuclei that continue to decay; fusion products are usually stable
Compare the size of a cation to its neutral atom, and explain why.
Cations are smaller because losing electrons reduces electron-electron repulsion and allows the nucleus to pull remaining electrons closer