General Chemistry: The Structure of the Atom and the Periodic Table

Flashcards covering the composition of the atom, atomic theory, subatomic particles, isotopes, atomic mass, the periodic table structure and trends, electron arrangement, orbitals, electron configuration, the octet rule, ion formation, and periodic properties like atomic size, ionization energy, and electron affinity.

What is an atom?

The basic structural unit of an element and the smallest unit of an element that retains the chemical properties of that element.

Describe the nucleus of an atom.

A small, dense, positively charged region in the center of the atom containing protons (positively charged particles) and neutrons (uncharged particles).

What are the three primary particles that atoms consist of?

Protons, neutrons, and electrons.

Describe the characteristics of electrons in an atom.

Negatively charged particles located outside of the nucleus, moving very rapidly in a relatively large volume of space.

When is an atom considered neutral?

A neutral atom (no electrical charge) has the same number of protons and electrons.

What does the atomic number (Z) represent?

The number of protons in the atom.

What does the mass number (A) represent?

The sum of the number of protons and neutrons.

How do you calculate the number of neutrons in an atom?

Number of neutrons = mass number - number of protons (or A - Z).

What is the charge and approximate mass (in amu) of a proton?

Charge: +1, Mass: 1.007 amu.

What is the charge and approximate mass (in amu) of a neutron?

Charge: 0, Mass: 1.009 amu.

What is the charge and approximate mass (in amu) of an electron?

Charge: -1, Mass: 5.486 x 10^-4 amu.

What are isotopes?

Atoms of the same element having different masses, meaning they contain the same number of protons but different numbers of neutrons.

What is atomic mass?

The weighted average of the masses of all the isotopes that make up an element, corrected by the relative amounts of each isotope present in nature.

According to Dalton's Atomic Theory, what is all matter composed of?

Tiny particles called atoms.

What did Dalton's Atomic Theory state about the creation, division, or destruction of an atom?

An atom cannot be created, divided, destroyed, or converted to any other type of atom.

What did Dalton's Atomic Theory state about atoms of a particular element?

Atoms of a particular element have identical properties.

According to Dalton's Atomic Theory, how do atoms of different elements differ?

Atoms of different elements have different properties.

How do atoms of different elements combine to form compounds, according to Dalton's Atomic Theory?

They combine in simple whole-number ratios to produce compounds.

What does chemical change involve, according to Dalton's Atomic Theory?

Chemical change involves joining, separating, or rearranging atoms.

How were electrons first discovered?

Using the cathode ray tube.

Who discovered protons?

Goldstein.

When were neutrons postulated to exist and when were they demonstrated?

They were postulated in the 1920s but not demonstrated until 1932.

What was the main experiment that led to the understanding of the atomic nucleus?

Rutherford's 'Gold Foil Experiment'.

What were the key conclusions drawn from Rutherford's Gold Foil Experiment?

Most of the atom is empty space, and the majority of the mass is located in a small, dense region (the nucleus).

How did Rutherford describe the atom?

A tiny, dense, positively charged nucleus of protons surrounded by electrons.

What is spectroscopy used for?

The study of information obtained from absorption or emission of light by atoms, used to understand electronic structure.

How does electromagnetic radiation travel and at what speed?

It travels in waves from a source at a speed of 3.0 x 10^8 m/s.

What is wavelength?

The distance between identical points on successive waves of light.

What is the relationship between the energy and wavelength of light?

High energy light has a short wavelength, and low energy light has a long wavelength.

According to the Bohr atom model, how do atoms absorb and emit energy?

Atoms absorb energy via promotion of electrons to higher energy levels and emit energy upon relaxation to lower levels.

What is an emission spectrum?

Light emitted when a substance is excited by an energy source, providing information about the electronic structure of the atom.

In Bohr's model, what happens when an electron absorbs energy?

It gets promoted to a higher energy level, reaching an excited state.

In Bohr's model, what happens when an electron travels back to lower energy levels?

Energy is released as a specific wavelength of light.

What is the ground state of an electron?

The lowest possible energy state for an electron.

What are quantized energy levels in Bohr's theory?

Allowed energy levels where electrons are found exclusively.

What was a major failure of Bohr's model of the atom?

It failed to explain the line spectra of atoms with more than one electron and suggested electrons move in fixed orbits, which is not accurate.

In modern atomic theory, what are atomic orbitals?

Regions in space with a high probability of finding an electron, where electrons move rapidly giving high electron density.

Who independently developed the precursor to the modern Periodic Table?

Dmitri Mendeleev and Lothar Meyer.

What is the Periodic Law?

The physical and chemical properties of the elements are periodic functions of their atomic numbers.

What is a period in the periodic table?

A horizontal row of elements.

What is a group (or family) in the periodic table?

A column of elements, where elements often share many similarities.

How are metals classified based on electron behavior?

Elements that tend to lose electrons during chemical change, forming positive ions.

How are nonmetals classified based on electron behavior?

Elements that tend to gain electrons during chemical change, forming negative ions.

What are metalloids?

Elements that have properties intermediate between metals and nonmetals.

List some key properties of metals.

High thermal and electrical conductivities, high malleability and ductility, metallic luster, and solid at room temperature (generally).

List some key properties of nonmetals.

Brittle, powdery solids or gases, and generally opposite properties to metals.

What information is typically provided by the atomic number on the periodic table?

The number of protons in the nucleus of an atom, also known as the nuclear charge.

Why is electron arrangement crucial in understanding how atoms form compounds?

It is the primary factor in understanding how atoms join together to form compounds.

What are valence electrons?

The outermost electrons in an atom, which are involved in chemical bonding.

Who developed equations that accounted for both the particle and wave nature of electrons?

Schrödinger.

What do Schrödinger's equations determine regarding electrons?

The probability of finding an electron in a specific region in space (quantum mechanics), defining principal energy levels, sublevels, and atomic orbitals.

What do principal energy levels (n) indicate about an electron?

The higher the value of n, the higher the energy level and the farther away from the nucleus the electrons are.

How is the number of sublevels in a principal energy level determined?

The number of sublevels in a principal energy level is equal to n.

What is the formula for the electron capacity of a principal energy level?

2(n)^2, where n is the principal energy level.

What is a sublevel (or subshell)?

A set of energy-equal orbitals within a principal energy level.

In what order do subshells increase in energy?

s < p < d < f.

What is an atomic orbital?

A specific region of a sublevel containing a maximum of two electrons.

What is the characteristic shape of an s orbital?

Spherically symmetrical.

What is the characteristic shape of a p orbital?

Much like a dumbbell.

What is electron configuration?

The arrangement of electrons in atomic orbitals.

What is the Aufbau Principle?

It states that electrons fill the lowest-energy orbital that is available first.

What is the Pauli Exclusion Principle?

Each orbital can hold up to two electrons with their spins in opposite directions (paired).

What is Hund's Rule?

Each orbital in a subshell is half-filled (with one electron) before any orbital becomes completely filled (with two electrons).

How many electrons can the s, p, and d sublevels hold, respectively?

The s sublevel can hold two electrons; the p sublevel can hold six electrons; the d sublevel can hold ten electrons.

How can a shorthand electron configuration be written?

By using the symbol of the preceding noble gas in brackets to represent the electrons in the filled inner shells, followed by the configuration of the valence electrons.

Why are noble gases considered extremely stable?

Due to a full complement of valence electrons in their outermost s and p sublevels.

What is the Octet Rule?

Elements usually react in such a way as to attain the electron configuration of the noble gas closest to them in the periodic table.

What is a stable electron configuration called when referring to the octet rule?

The 'noble gas' configuration.

What are ions?

Electrically charged particles that result from a gain or loss of one or more electrons by the parent atom.

What is a cation and how is it formed?

A positively charged ion that results from the loss of electrons.

What is an anion and how is it formed?

A negatively charged ion that results from the gain of electrons.

How do metallic elements tend to form ions?

Metallic elements tend to lose all their valence electrons to obtain a configuration of the nearest noble gas, forming positively charged cations.

How do nonmetallic elements tend to form ions?

Nonmetallic elements tend to gain valence electrons to obtain a configuration of the nearest noble gas, forming negatively charged anions.

For atoms within the same group, how does the number of electrons lost when forming cations relate?

All atoms of a group tend to lose the same number of electrons when forming ions.

What is characteristic about ion formation in transition metals?

Transition metals often form more than one stable ion, making it harder to predict the charge directly from octet rules.

What does it mean for atoms or ions to be 'isoelectronic'?

They have the same number of electrons.

What atomic properties correlate with electronic structure and position on the periodic table?

Atomic size, ion size, ionization energy, and electron affinity.

How does atomic size change when moving down a group in the periodic table, and why?

Atomic size increases moving down a group because the valence shell is higher in energy and farther from the nucleus.

How does atomic size change when moving from left to right across a period in the periodic table, and why?

Atomic size decreases from left to right across a period because the increase in positive charge in the nucleus pulls the electrons closer to the nucleus.

How does the size of a cation compare to its parent atom, and why?

Cations are smaller than their parent atom because they have more protons than electrons, creating an increased nuclear charge that pulls remaining electrons closer, and often a valence shell is lost.

How does the size of an anion compare to its parent atom, and why?

Anions are larger than their parent atom because they have more electrons than protons, meaning the excess negative charge reduces the pull of the nucleus on each individual electron.

What is ionization energy?

The energy required to remove an electron from an isolated atom.

What does a lower ionization energy indicate?

The easier it is to form a cation.

How does ionization energy change when moving down a family (group)?

Ionization energy decreases down a family because the outermost electrons are farther from the nucleus and less tightly held.

How does ionization energy change when moving across a period?

Ionization energy increases across a period because the outermost electrons are more tightly held due to increased nuclear charge.

What is electron affinity?

The energy released when a single electron is added to an isolated atom.

What does a large electron affinity indicate?

An atom becomes more stable as it forms an anion.

How does electron affinity generally change when moving down a group?

Electron affinity generally decreases down a group.

How does electron affinity generally change when moving across a period?

Electron affinity generally increases across a period.