Atomic Structure
What do we call the outermost electrons that determine an element’s chemical behavior?
Valence electrons
Who created the first organized periodic table?
Dmitri Mendeleyev.
What do we call a substance made of two or more elements chemically combined in a fixed ratio?
A compound
What is electricity?
The flow of electrons
What does voltage represent?
The electrical pressure that pushes electrons
How many electrons can the first and second electron shells hold?
2 in the first shell, 8 in the second
What does the atomic number of an element represent?
The number of protons in its nucleus.
What does a chemical formula show?
The number and types of atoms in a compound.
In a neutral atom, what must be equal?
The number of protons and electrons.
What do we call materials that allow electrons to flow easily, like copper?
Conductors.
Why are noble gases almost completely non-reactive?
Their valence shells are already full, making them stable.
What is the group name for highly reactive nonmetals like fluorine and chlorine?
The Halogens.
What does the word “aqueous” mean?
The substance is dissolved in water
If an object loses electrons, what type of charge does it gain?
A positive charge.
State Ohm’s Law.
Voltage = Current × Resistance.
What happens to a metal atom with 1–3 valence electrons when it reacts?
It tends to lose electrons and form a positive ion (cation)
Why do elements in the same group have similar chemical properties?
They have the same number of valence electrons
A substance that cannot be broken down by chemical means is called what?
An element.
What must happen for electricity to shock you?
A complete circuit must be formed
Why doesn’t a bird get shocked on a power line?
It touches only one point and has no path to the ground.
Group 17 elements all behave similarly. What feature gives them these similar chemical properties?
They all have 7 valence electrons
Which type of elements tend to be brittle and poor conductors?
Nonmetals.
Why is H₂O a compound but O₂ is not?
H₂O has different elements chemically bonded; O₂ is only one element
Why does static electricity occur when touching a doorknob?
Extra electrons discharge rapidly from one object to another.
If resistance increases while voltage stays the same, what happens to current?
The current decreases.