Atomic Structure and Subatomic Particles

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Questions and Answers

Which statement correctly describes the role of electrons in an atom?

Electrons have mass and reside in the nucleus.

Electrons are negatively charged particles that orbit the nucleus. (correct)

Electrons are positively charged particles that circle the nucleus.

Electrons determine the mass of the atom.

What defines the type of a particular atom?

The charge of the neutrons.

The number of protons found in the nucleus. (correct)

The number of neutrons present in the atom.

The mass of the electrons surrounding the nucleus.

Which of the following statements about neutrons is true?

Neutrons are negatively charged particles.

Neutrons help define an isotope of an atom. (correct)

Neutrons positively charge the atom.

Neutrons have mass but no charge. (correct)

What does Dalton’s Postulates state regarding chemical reactions?

Atoms are neither created nor destroyed in chemical reactions. Signup and view all the answers

What makes up most of the mass of the atom?

Protons and neutrons together. Signup and view all the answers

What would happen to a compound if the number of atoms of each element changes?

It will not be considered a compound any longer. Signup and view all the answers

Which charge do protons carry?

Positive charge. Signup and view all the answers

If an atom gains an electron, what happens to its overall charge?

It becomes negatively charged. Signup and view all the answers

What is the molar mass of magnesium nitrate, Mg(NO3)2?

148.33 g/mol Signup and view all the answers

How many grams of titanium are in 1.33 moles?

63.7 g Signup and view all the answers

What is the calculated number of sodium atoms in 10 g of sodium?

2.62 × 10^23 atoms Na Signup and view all the answers

What is the molar mass of oxygen gas O2?

32.00 g/mol Signup and view all the answers

How many grams are yielded from 2.55 × 10^23 atoms of lead?

87.8 g Pb Signup and view all the answers

What is the atomic mass of iron in grams per mole?

55.85 g/mol Signup and view all the answers

Using Avogadro's number, how many O2 molecules are present in 0.470 g of oxygen gas?

1.47 × 10^22 molecules O2 Signup and view all the answers

What is the relationship between atomic mass and the number of grams in one mole of an element?

Atomic mass equals the grams in one mole for each element. Signup and view all the answers

How many neutrons are present in a carbon isotope with a mass number of 14?

8 Signup and view all the answers

What is Avogadro's Number?

6.022 × 10^23 Signup and view all the answers

If you have 0.5 mol of sodium (Na), how many sodium atoms do you have?

3.01 × 10^23 Signup and view all the answers

How many moles are represented by 1.25 × 10^21 atoms of potassium (K)?

2.08 × 10^-3 Signup and view all the answers

What is the molar mass of iron (Fe)?

55.85 g/mol Signup and view all the answers

Which of the following correctly describes the concept of a mole?

A quantity of 6.022 × 10^23 particles. Signup and view all the answers

How many electrons are typically found in a neutral atom of carbon?

6 Signup and view all the answers

What does the term 'molar mass' refer to?

The atomic mass in grams of an element. Signup and view all the answers

How many grams of O3 are in 3.36 L of O3 at STP?

7.20 g O3 Signup and view all the answers

What is the chemical formula for niacin, which contains 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom?

C6H6N2O Signup and view all the answers

What is the percent composition of oxygen in water (H2O)?

89% oxygen Signup and view all the answers

If the mass of ammonium nitrate (NH4NO3) is 80 g/mol, what is the percent composition of nitrogen (N)?

35% N Signup and view all the answers

What is the number of molecules of hydrogen gas (H2) present in 0.500 L at STP?

1.34 × 10^22 molecules H2 Signup and view all the answers

What primarily indicates the number of each type of atom in a chemical formula?

Subscript following the atom symbol Signup and view all the answers

For the compound TNT (C7H5(NO2)3), what would you need to calculate the percent composition of nitrogen?

Molecular mass of TNT Signup and view all the answers

Which of the following statements is true about a chemical formula?

It expresses types and numbers of atoms in a molecule Signup and view all the answers

What is the percent composition of carbon in TNT?

37.01% Signup and view all the answers

Which formula represents the empirical formula of benzene?

CH Signup and view all the answers

How is the empirical formula for a compound determined from percent composition?

By using the masses of the elements to calculate the moles. Signup and view all the answers

What is the empirical formula for octane?

C4H9 Signup and view all the answers

If the empirical formula of a substance is CH, what can be said about its molecular formula?

It can be (CH)n for some integer n. Signup and view all the answers

What is the total mass of TNT calculated from its components?

227.15 g Signup and view all the answers

What does the molecular formula indicate about a compound?

It gives the exact number of atoms of each element. Signup and view all the answers

What ratio of elements is represented in the empirical formula derived from 92.2 g of carbon and 7.83 g of hydrogen?

C1.00H1.01 Signup and view all the answers

Study Notes

Electrons

Small, negatively charged particles
Orbit the nucleus
Have no mass
Number of electrons = number of protons

Protons

Small, positively charged particles
Located in the nucleus
They, along with neutrons, make up most of the mass of the atom
The number of protons defines the type of atom
Number of protons = number of electrons

Neutrons

Small, neutrally charged particles
Located in the nucleus
They, along with protons, make up most of the mass of the atom
A differing number of neutrons defines an "isotope" of an atom

Properties of Subatomic Particles

Particle	Mass (kg)	Mass (amu)	Charge
Electron	9.10939 x 10^-31	0.00055	1-
Proton	1.67262 x 10^-27	1.00728	1+
Neutron	1.67493 x 10^-27	1.00866	0

Atomic Theory of Matter

The theory that atoms are the fundamental building blocks of matter reemerged in the early 19th century, championed by John Dalton.

Dalton's Postulates

Each element is composed of extremely small particles called atoms.
All atoms of a given element are identical to one another in mass and other properties, but the atoms of one element are different from the atoms of all other elements.
Atoms are neither created nor destroyed in chemical reactions; they are merely rearranged.
Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.

Dalton's Atomic Theory (1808)

Elements are composed of extremely small particles called atoms.
All atoms of a given element.
Compounds are composed of atoms of more than one element.

The Mole Concept

The mole is a unit of measure for an amount of a chemical substance.
Avogadro’s Number (symbol N) is the number of atoms in 12.01 grams of carbon.
A mole is Avogadro’s number of particles, that is 6.02 × 1023 particles.
We can use the mole relationship to convert between the number of particles and the mass of a substance.

The Mole

One mole = amount of any substance that contains as many particles of that substance as there are atoms of C in 12 g of pure carbon-12
1 mole = 6.022× 1023 particles = Avogadro’s Number
1 mole of Fe = 6.022× 1023 atoms of Fe
1 mole of H2O = 6.022× 1023 molecules of H2O

Mole Calculations

To convert from moles to atoms: Multiply by Avogadro's number (6.02 x 10^23)
To convert from atoms to moles: Divide by Avogadro's number (6.02 x 10^23)

Molar Mass

The atomic mass of any substance expressed in grams is the molar mass (MM) of that substance.
The atomic mass of iron is 55.85 amu.
The molar mass of iron is 55.85 g/mol.

Calculating Molar Mass

The molar mass of a substance is the sum of the molar masses of each element.

Atomic Mass

Atomic Mass (Atomic Weight) = number of grams in 1 mole of that element.

Mass-Mole Calculations

To convert from moles to grams: Multiply by the molar mass.
To convert from grams to moles: Divide by the molar mass.

Mole-Volume Calculations

To convert from liters at STP (Standard Temperature and Pressure) to moles: Divide by 22.4 L/mol.
To convert from moles to liters at STP: Multiply by 22.4 L/mol.
To convert from liters at STP to molecules: Multiply by Avogadro's number and then by the number of molecules in one mole (6.02 x 10^23).

Chemical Formulas

A molecule is composed of two or more nonmetal atoms.
A chemical formula expresses the number and types of atoms in a molecule.

Writing Chemical Formulas

The number of each type of atom in a molecule is indicated with a subscript in a chemical formula.
If there is only one atom of a certain type, no ‘1’ is used.

Percent Composition

The percent composition of a compound lists the mass percent of each element.
For example, the percent composition of water, H2O is: 11% hydrogen and 89% oxygen

Calculating Percent Composition

To find the percent composition of a compound, divide the mass of each element by the total mass of the compound and multiply by 100%.

Empirical Formulas

The empirical formula represents the simplest whole number ratio of ions in a formula unit or atoms of each element in a molecule.

Empirical Formulas from Percent Composition

Assume a 100 g sample and calculate the moles of each element.
Divide the moles of each element by the smallest number of moles.
The resulting numbers represent the subscripts in the empirical formula.

Molecular Formulas

The actual molecular formula is some multiple of the empirical formula.
To determine the molecular formula, find the empirical formula mass and divide the molecular mass by it.
The resulting number represents the multiple of the empirical formula.

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Description

This quiz focuses on the fundamental concepts of atomic structure, including the properties of subatomic particles such as electrons, protons, and neutrons. Additionally, it touches on Dalton's atomic theory and the significance of atomic composition in defining elements. Test your understanding of these essential topics in chemistry!