atoms and periodic table

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Questions and Answers

What term describes the spontaneous emission of particles and/or radiation from certain elements?

Ionization

Radioactivity (correct)

Decay

Radiation

Which type of radiation consists of positively charged particles?

Gamma rays

Alpha rays (correct)

Beta rays

X rays

What is the unit used to define the amount of a substance containing Avogadro's number of entities?

Atom

Mole (correct)

Mass

Volume

If 98.93% of carbon atoms in a sample are carbon-12, what is the mass of carbon-12?

12 u Signup and view all the answers

How is molar mass defined?

Mass of one mole of units of a substance Signup and view all the answers

Which particle type is deflected by a negatively charged plate?

Beta particles Signup and view all the answers

What is the currently accepted value for Avogadro's number?

6.022 x 10^23 Signup and view all the answers

What type of radiation is not affected by an external electric field?

Gamma rays Signup and view all the answers

What principle states that no two electrons can have the same set of four quantum numbers?

Pauli exclusion principle Signup and view all the answers

Which of the following correctly describes the filling order of orbitals?

1s, 2s, 2p, 3s, 3p, 4s Signup and view all the answers

According to Hund's Rule, how do electrons occupy degenerate orbitals?

Electrons occupy orbitals singly with parallel spins. Signup and view all the answers

How many electrons can occupy a single orbital according to the Pauli exclusion principle?

Two with opposite spins Signup and view all the answers

Which statement is true regarding the electronic configuration of Chlorine (Cl)?

Cl has a configuration of 1s22s22p63s23p5 Signup and view all the answers

Which group of elements has a general outer-shell electron configuration of ns2np5?

Halogens Signup and view all the answers

What are the vertical columns in the periodic table called?

Families Signup and view all the answers

What is the outermost electron configuration for the group 18 noble gases (excluding helium)?

ns2np6 Signup and view all the answers

Which block in the periodic table consists of groups 1 and 2 plus helium?

s block Signup and view all the answers

What effect does increasing atomic number have on atomic radius within a group?

Increases atomic radius Signup and view all the answers

How does the ionic radius of cations compare to the atomic radius of their corresponding atoms?

Cations are smaller Signup and view all the answers

Which trend is observed in ionization energies as one moves across a period from left to right?

Ionization energy increases Signup and view all the answers

Which electronic shell do the d orbitals fill?

n - 1 Signup and view all the answers

What happens to ionization energy as atomic radius increases?

Ionization energy decreases Signup and view all the answers

What is the shielding constant associated with?

Effective nuclear charge Signup and view all the answers

Mendeleev's periodic table was initially arranged based on which criterion?

Increasing atomic mass Signup and view all the answers

What is the definition of electron affinity?

Energy released when an atom gains an electron Signup and view all the answers

Which statement correctly describes the metalloids?

They possess properties that are a mix of metals and nonmetals. Signup and view all the answers

What characterizes the physical properties of metals?

Shiny, ductile, and malleable Signup and view all the answers

How is the effective nuclear charge (Zeff) calculated?

Z - sigma Signup and view all the answers

Which of the following correctly defines the f-block elements?

Elements that are the lanthanides and actinides Signup and view all the answers

What key concept did Max Planck introduce in 1900 regarding the emission of energy by atoms?

Energy is emitted in specific discrete quantities. Signup and view all the answers

Nonmetals are generally characterized by which of the following properties?

They are poor conductors of heat and electricity. Signup and view all the answers

Which statement correctly describes the relationship between energy levels in quantum theory?

The difference between allowed energies is called a quantum of energy. Signup and view all the answers

What phenomenon occurs when light strikes certain metals according to Heinrich Hertz's discovery?

Electrons are ejected from the metal's surface. Signup and view all the answers

What distinguishes the majority of elements on the periodic table?

They are classified as metals. Signup and view all the answers

In the modern periodic table, the elements are arranged based on which principal characteristic?

Increasing atomic number Signup and view all the answers

Which of the following statements is true regarding the photoelectric effect?

Kinetic energy of emitted electrons is dependent on frequency of light. Signup and view all the answers

How did Albert Einstein contribute to the understanding of electromagnetic radiation?

He introduced the concept of wave-particle duality. Signup and view all the answers

What is the relationship between the frequency of light and the energy of a photon as given by the formula proposed by Einstein?

Energy is directly proportional to frequency. Signup and view all the answers

What does wavelength refer to in the context of wave properties?

The distance between identical points on successive waves. Signup and view all the answers

According to quantum theory, what is the nature of energy as compared to classical physics?

Energy is limited to specific values in quantum theory. Signup and view all the answers

Study Notes

Radioactivity

Marie Curie named the spontaneous emission of particles and radiation from elements as radioactivity.
Radioactive elements emit three types of rays: Alpha (α), Beta (β) and Gamma (γ)
α rays are positively charged particles deflected by positively charged plates.
β rays are electrons deflected by negatively charged plates.
γ rays are high-energy rays that have no charge and are not affected by external fields.

Average Atomic Mass

The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its abundance.
For example, Carbon-12 has a mass of 12 u and Carbon-13 has a mass of 13.0033548378 u. In a sample, 98.93% of Carbon atoms are Carbon-12 and the remaining are Carbon-13.

Mole (mol)

Mole is the SI unit for the amount of substance containing as many elementary entities as there are atoms in exactly 12 g (or 0.012 kg) of carbon-12.
The number of atoms in 12 g of carbon-12 is called Avogadro’s number (N A ) and its currently accepted value is 6.022 x 10^23.

Molar Mass

Molar Mass (m) is the mass in grams or kilograms of 1 mole of units of a substance, such as atoms or molecules.
The molar mass of carbon-12 is 12.00 g and 1 mole of carbon-12 contains 6.022 x 10^23 atoms.

Quantum Theory

Max Planck discovered that atoms and molecules emit energy in discrete quantities called quanta.
Classical Physics dictates that energy is continuous, while Quantum Theory limits energy to specific values.
The difference between permitted energy levels of a system is called a quantum of energy and determines the energy increase when transitioning between those levels.

Nature of Light

Heinrich Hertz discovered the photoelectric effect: electrons are ejected when light strikes the surface of certain metals.
Electrons are only emitted when the incident light frequency exceeds a threshold value.
The number of emitted electrons is proportional to the intensity of the light, while their kinetic energy depends on the light frequency.
Albert Einstein proposed that light has particle-like qualities and that these particles have characteristic energy given by Ephoton = hv, where v is the frequency of light and h is Planck's constant.
Planck’s constant is denoted by h and its value is 6.62607 x 10^-34 J s.

Properties of Waves

A wave is a vibrating disturbance through which energy is transmitted.
Wavelength (λ) is the distance between identical points on successive waves.

Electronic Configuration

Electrons occupy orbitals in a manner that minimizes the energy of the atom.
Aufbau principle states that the total energy of an atom depends on orbital energies and electronic repulsion, with orbitals generally filling in the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.
Pauli Exclusion Principle states that no two electrons in an atom can have the same set of four quantum numbers, meaning only two electrons with opposite spins can occupy the same orbital.
Hund's rule states that for degenerate orbitals, electrons will initially occupy orbitals singly with parallel spins.

Electron Configuration and the Periodic Table

Alkali metals have one valence electron in an s orbital.
Halogens have seven valence electrons in the configuration ns^2np^5.
Noble gases have eight valence electrons in the configuration ns^2np^6, except for Helium which has only two electrons.

Blocks of Elements

Elements can be classified into four blocks based on the subshells being filled:
- s block: The highest principal quantum number (n) s orbital fills, including groups 1 and 2, plus Helium.
- p block: The highest quantum number (n) p orbitals fill, including groups 13, 14, 15, 16, 17, and 18 (except He).
- d block: The (n-1) d orbitals fill, encompassing groups 3 through 12.
- f block: The (n-2) f orbitals fill, including the lanthanides and actinides.

Modern Periodic Table

Dmitri Mendeleev arranged elements in order of increasing atomic mass, which closely resembles the modern periodic table.
Elements were later rearranged in order of increasing atomic number.

Element Classification

Elements are broadly classified into:
- Metals: Found to the left of the periodic table, with the exception of hydrogen. They tend to lose electrons, are solid at room temperature (except mercury), shiny with good conductivity of heat and electricity, and are ductile and malleable.
- Nonmetals: Found to the right of the periodic table, they tend to gain electrons, are brittle with poor conductivity, and are not malleable or ductile.
- Metalloids: Located along the stair-stepped line in the periodic table, they have intermediate properties of metals and nonmetals, and are valuable semiconductors.

Periodic Properties

Periods: The seven horizontal rows of the periodic table. Elements within a period have increasing atomic numbers from left to right.
Groups/Families: Vertical columns in the periodic table, labeled using Roman numerals and letters (older) or numbers 1 through 18 (newer).

Effective Nuclear Charge

The effective nuclear charge (Zeff) is the net positive charge experienced by an electron in an atom.
Zeff = Z - σ, where Z is the actual nuclear charge and σ is the shielding constant, representing the repulsion from other electrons.

Atomic Properties

Atomic Radius: Defined as half the distance between the nuclei of two adjacent atoms in a molecule or metal. Atomic radius increases down a group.
Ionic Radius: The radius of a cation or anion.
- Cations are smaller than their corresponding atoms
- Anions are larger than their corresponding atoms
- For isoelectronic ions, the ionic radius decreases with increasing positive charge and increases with increasing negative charge.
Ionization Energy (Ei): The energy required to remove an electron from a gaseous atom. Ionization energy generally increases across a period and decreases down a group.
Electron Affinity (Eea): The enthalpy change when an atom in the gas phase gains an electron.

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Description

Test your knowledge on radioactivity, the properties of alpha, beta, and gamma rays, as well as the concept of average atomic mass and moles. This quiz will cover essential concepts related to these fundamental topics in chemistry.