Chapter 4 Sections 2 & 3 Science - Abigail Morales

What is the difference between protons, neutrons, and electrons?

What is the difference between protons, neutrons, and electrons?

The three main subatomic particles are distinguished by mass, charge, and location in the atom.

What is an atom?

Each element has a unique number of protons.

Unreacted atoms have no overall charge.

Because there is an equal number of protons and electrons, the charges cancel out.

The electric force holds the atom together.

Positive protons are attracted to negative electrons by the electric force.

This force holds the atom together.

What do atoms of an element have in common with other atoms of the same element?

Atoms of each element have the same number of protons, but they can have different numbers of neutrons.

Atomic Number

the number of protons in the nucleus of an atom

Mass Number

the sum of the numbers of protons and neutrons in the nucleus of an atom

What does the atomic number equal?

The atomic number equals the number of protons.

What does the mass number equal?

The mass number equals the total number of subatomic particles in the nucleus.

Why do isotopes of the same element have different atomic masses?

Isotopes of an element vary in mass because their numbers of neutrons differ.

radioisotopes

unstable isotopes that emit radiation and decay into other isotopes

How can the number of neutrons be calculated?

number of neutrons = mass number – atomic number

What unit is used to express atomic mass?

Because working with such tiny masses is difficult, atomic masses are usually expressed in unified atomic mass units.

unified atomic mass unit

a unit of mass that describes the mass of an atom or molecule; it is exactly 1/12 the mass of a carbon atom with mass number 12 (symbol, u)

How is atomic mass weighted?

Average atomic mass is a weighted average.

isotope abundance determines the average atomic mass.

Example: Chlorine-35 is more abundant than chlorine-37, so chlorine’s average atomic mass (35.453 u) is closer to 35 than to 37.

mole

the SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly 12 g of carbon-12 (abbreviation, mol)

1 mol = 602, 213, 670, 000, 000, 000, 000, 000 particles

What is Avogadro’s number?

6.022 × 1023 (23 power)

molar mass

the mass in grams of one mole of a substance

What can you convert molar mass between?

You can convert between moles and grams.

Modern Models of the Atom

In the modern atomic model

Electrons can be found only in certain energy levels

Not between levels

Furthermore, the location of electrons cannot be predicted precisely.

What are electron levels limited to?

electron location

What happens when electrons move up level?

In Bohr’s model, electrons can be in only certain energy levels.

They gain energy to move to a higher energy level or lose energy to move to a lower energy level.

What do electrons act like?

Waves

Can the exact location of an atom be located?

No

Orbital

a region in an atom where there is a high probability of finding electrons

How are the energy levels of an atom filled?

The number of energy levels that are filled in an atom depends on the number of electrons.

Valence Electron

an electron that is found in the outermost shell of an atom and that determines the atom’s chemical properties

What are the four types of orbitals?

Orbital types are s, p, d, and f.

Each orbital can hold 2 electrons.

What do orbitals determine?

Orbitals determine the number of electrons that each level can hold.

Order of Fill of Orbitals

What makes an electron jump to a new energy level?

Electrons jump between energy levels when an atom gains or loses energy.

The lowest state of energy of an electron is called the

ground state

If an electron gains energy by absorbing a photon, it moves to an

excited state

photon

a unit or quantum of light

When does an electron release a photon?

The electron releases a photon when it falls back to a lower level.

How do the energies from photons correspond to an electron jumping?

Photons have different energies. The energy of a photon corresponds to the size of the electron jump.

How many protons and neutrons does a silicon, Si, have and where are these located?

14 Protons and 14 Neutrons in the most common isotope of Silicon. They are located in the nucleus. It has 14 Electrons in a neutral atom.

Explain why different atoms of the same element always have the same atomic number but can have different masses.

The atomic number is the number of protons in an atom. All atoms of the same element have the same number of protons. The mass of an element is the total number of protons and neutrons in the nucleus. The number of neutrons may vary among atoms of the same element. These are called Isotopes.

What does an elements molar mass tell you about the element?

The molar mass is the mass of one mole, or 6.022 x 1023 particles, of the element.

What is an orbital?

An orbital is a region in the atom where there is a high probability of finding electrons.

If an atom has a mass of 11u and contains five electrons, its atomic number must be _____

5

Which statement is not true of Bohr’s model for the atom.

a. Electrons cannot be between energy levels

b. Electrons orbit the nucleus.

c. An electrons path is not known exactly

d. Electrons exist in energy levels.

C – An electron’s path is not known exactly.

According to the modern model of the atom,

a. Moving electrons form an electron cloud.

b. Electrons and protons circle neutrons.

c. Neutrons have a positive charge.

d. The number of protons for a given element varies.

a – moving electrons form an electron cloud.

Carbon has six protons. How many valence electrons does it have?

4

The second energy level has 1 s orbital and 3 p orbitals. How many electrons can this level hold?

8

An electron moves from the ground state to an excited state when it absorbs a ______.

photon

Identify the parts of an atom.

The particles that make up an atom are protons, neutrons, and electrons. The number of protons determines the atom’s atomic number. In a neutral atom number also equals the number of electrons.

Determine the atomic number and mass number of an isotope that has 56 electrons and 82 neutrons.

Atomic Number = 56

Atomic Mass = 138

Why do most atoms have no charge even though they are made up of positively charged protons and negatively charged electrons?

Most atoms have no overall charge because they have equal numbers of protons and electrons, so the positive and negative charges exactly cancel one another.

Are hydrogen-3 and helium-3 isotopes of the same element? Explain.

They are not isotopes of the same element. They have the same mass number, but different numbers of protons. It is the number of protons that defines the element.

For an experiment you have been asked to do, you need 1.5g of iron. How many moles of iron do you need?

0.027 mol Fe

Robyn recycled 15.1 moles of aluminum last month. What is the mass in grams of the aluminum she recycled?

407 g Al