Chemistry Flashcards
What are atoms?
The basic units of matter made up of protons, neutrons, and electrons.
What is the nucleus of an atom?
The dense center of an atom containing protons and neutrons.
What are electrons and where are they found?
Negatively charged particles found in shells (energy levels) around the nucleus.
What defines an element?
A substance made of only one type of atom, with a specific number of protons.
How are elements represented?
By chemical symbols, e.g., H for hydrogen and O for oxygen.
What is a compound?
A substance formed when two or more elements chemically bond.
How do compounds differ from mixtures?
Compounds have fixed ratios and are chemically bonded, while mixtures are physically combined.
What is a reactant in a chemical reaction?
A substance present at the start of a reaction.
What is the product in a chemical reaction?
The substance formed after the reaction.
What was Dalton’s atomic theory?
All matter is made of indivisible atoms, which combine in fixed ratios.
What did J.J. Thomson discover?
The electron, leading to the plum pudding model of the atom.
What was Rutherford’s gold foil experiment?
It showed atoms have a dense, positive nucleus surrounded by empty space.
How did Bohr improve the atomic model?
He proposed electrons orbit the nucleus in fixed energy levels.
How did Mendeleev organize the periodic table?
By increasing atomic mass and grouping elements by similar properties.
What key change occurred in the modern periodic table?
It is organized by atomic number, not mass.
What are groups in the periodic table?
Vertical columns that contain elements with similar chemical properties.
What are periods?
Horizontal rows that show elements with the same number of electron shells.
What trend occurs across a period?
Atomic size decreases, and elements become less metallic.
What are properties of metals?
Conduct electricity, malleable, ductile, shiny, and high melting points.
What are properties of non-metals?
Poor conductors, brittle, dull, and low melting points.
Why are Group 1 metals so reactive?
They have one electron in their outer shell, which is easily lost.
What happens when alkali metals react with water?
They produce hydrogen gas and an alkaline solution.
How does reactivity change down Group 1?
Reactivity increases because the outer electron is farther from the nucleus.
What are the states of halogens at room temperature?
Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid.
What is displacement in halogens?
A more reactive halogen displaces a less reactive halogen from its compounds.
How does reactivity change down Group 7?
Reactivity decreases as it is harder to attract electrons.
Why are noble gases unreactive?
They have full outer electron shells.
How do boiling points change down Group 0?
Boiling points increase due to stronger intermolecular forces.
What is an ion?
An atom or group of atoms with a positive or negative charge.
How do metals form ions?
By losing electrons to form positive ions (cations).
How do non-metals form ions?
By gaining electrons to form negative ions (anions).
What is ionic bonding?
The transfer of electrons between a metal and a non-metal.
What holds ionic compounds together?
Strong electrostatic forces between oppositely charged ions.
What are properties of ionic compounds?
High melting points, soluble in water, and conduct electricity when molten or dissolved.
What is covalent bonding?
The sharing of electrons between two non-metals.
What is a single covalent bond?
One pair of shared electrons.
What are simple molecular substances?
Small molecules with strong covalent bonds but weak intermolecular forces.
Why do simple molecular substances have low boiling points?
Weak intermolecular forces require little energy to overcome.
What are examples of giant covalent structures?
Diamond, graphite, and silicon dioxide.
Why is diamond hard?
Each carbon atom forms four strong covalent bonds.
Why does graphite conduct electricity?
It has delocalized electrons between its layers.
Why does reactivity increase down Group 1?
The outer electron is farther from the nucleus, making it easier to lose.
Why does reactivity decrease down Group 7?
Attracting an extra electron becomes harder due to increased shielding.
Why do noble gases have higher boiling points as you go down the group?
Larger atoms have stronger intermolecular forces.
What is the significance of the periodic table’s organization?
It predicts element properties and reactions.
How does atomic size change across a period?
It decreases due to increased nuclear charge pulling electrons closer.
What are alloys and why are they useful?
Mixtures of metals to improve strength, corrosion resistance, or other properties.
