Chapter 1 – Atoms and Elements EST Flashcards
(16 cards)
What is an isotope?
Atoms of the same element with the same number of protons but different numbers of neutrons.
Why is the atomic mass of elements not a whole number?
It is a weighted average of all natural isotopes (relative atomic mass).
What is a mole?
6.022 x 10²³ particles (Avogadro’s number).
What is the molar mass?
The mass in grams of one mole of a substance.
How many moles are in 36 grams of carbon? (Molar mass = 12 g/mol)
36 ÷ 12 = 3 moles
What is the mass of 2 moles of Na (molar mass = 23 g/mol)?
2 × 23 = 46 g
How many hydrogen atoms in 3 moles of H₂O?
3 × 2 × 6.022×10²³ = 3.613×10²⁴ atoms
What is periodicity of properties?
The repeating patterns of element properties across periods.
What is atomic radius and how does it trend?
Size of the atom; decreases across a period, increases down a group.
What happens to chemical reactivity in metals down a group?
It increases (easier to lose electrons).
What happens to chemical reactivity in non-metals up a group?
It increases (stronger attraction for electrons).
What is the simplified atomic model?
A model showing protons, neutrons, electrons, and electron shells with number labels.
What is the Lewis diagram?
A model showing only the valence electrons of an atom.
How many neutrons in Carbon-14?
14 - 6 = 8 neutrons
What is the molar mass of glucose (C₆H₁₂O₆)? (C=12.01, H=1.008, O=16)
6×12.01 + 12×1.008 + 6×16 = 180.16 g/mol
How many molecules in 2 moles of NaCl?
2 × 6.022×10²³ = 1.204×10²⁴ molecules
