Atom Stucture
Which subatomic particle has a positive charge?
Proton
A neutral carbon-14 atom has an atomic number of 6. How many protons, neutrons, and electrons does it have?
6 protons, 8 neutrons, 6 electrons
Which scientist proposed the “plum pudding” model, with electrons embedded in a positively charged material?
J. J. Thomson
How many representative particles are in one mole of a substance?
6.02 x 1023 particles
What does an element’s atomic number tell you?
The number of protons in each atom
Which subatomic particle has no charge, and where is it located?
A neutron; in the nucleus
A sodium ion, Na⁺, has an atomic number of 11 and a mass number of 23. How many protons, neutrons, and electrons does it have?
11 protons, 12 neutrons, 10 electrons
Dalton pictured atoms as solid, indivisible spheres. Which later discovery showed that atoms contain smaller particles?
The discovery of the electron
What is the molar mass of CaCl₂?
110.98 g/mol
How do you calculate an atom’s mass number?
Add its protons and neutrons.
Where are electrons located, and what charge do they have?
In the electron cloud outside the nucleus; negative
A sulfur ion, S²⁻, has an atomic number of 16 and a mass number of 32. How many protons, neutrons, and electrons does it have?
16 protons, 16 neutrons, 18 electrons
In Rutherford’s gold foil experiment, most alpha particles passed straight through the foil. What did this reveal about atoms?
Atoms are mostly empty space.
What mass, in grams, is equal to 2.50 mol of aluminum?
67.5 g Al
Why is the atomic mass on the periodic table usually a decimal instead of a whole number?
It is a weighted average of the masses of the element’s naturally occurring isotopes
An atom is mostly empty space. Where is nearly all of its mass concentrated, and which particles account for that mass?
In the nucleus; protons and neutrons
An ion has 20 protons, 22 neutrons, and 18 electrons. Identify the element, its mass number, and its charge
Calcium; mass number 42; 2+
A few alpha particles in Rutherford’s experiment were strongly deflected or bounced back. What did this suggest about the nucleus?
It is small, dense, and positively charged.
How many moles are in 36.0 g of water, H₂O?
2.00 mol H₂O
An element has two naturally occurring isotopes: one with a mass of 10 amu and 20% abundance, and another with a mass of 11 amu and 80% abundance. Calculate its average atomic mass.
10.8 amu
A neutral atom has 13 electrons. How many protons does it have, and which element is it?
13 protons; aluminum
Particle A has 17 protons, 18 neutrons, and 18 electrons. Particle B has 17 protons, 20 neutrons, and 17 electrons. Are they isotopes of the same element? Give the mass number and charge of each.
Yes. A: chlorine-35, 1−. B: chlorine-37, neutral.
How does the modern electron cloud model differ from Bohr’s model in its description of electron locations?
Bohr placed electrons in fixed orbits at specific energy levels. The modern model describes regions where electrons are likely to be found, rather than fixed paths.
A copper sample has a mass of 12.7 g. How many copper atoms does it contain?
1.20 x 1023 atoms Cu
An element has two isotopes with masses of 63 amu and 65 amu. Its average atomic mass is 63.4 amu. Which isotope is more abundant, and what is its percent abundance?
An element has two isotopes with masses of 63 amu and 65 amu. Its average atomic mass is 63.4 amu. Which isotope is more abundant, and what is its percent abundance?