Chemistry Unit 8: Importance of Electrons

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Questions and Answers

How do different elements' electrons respond to energy absorption?

All elements absorb the same amount of energy.

Only non-metals can absorb energy.

Metals do not absorb energy at all.

Different elements absorb different amounts of energy due to their unique electron configurations. (correct)

Which scientist proposed that electrons occupy fixed orbits around the nucleus?

Bohr (correct)

Schrodinger

Rutherford

Thomson

What does the octet rule state regarding electron distribution in an atom?

Atoms can hold an unlimited number of electrons.

Electrons fill the orbits nearest to the nucleus first. (correct)

Electrons do not need to fill any orbits.

Electrons fill the outermost shell first.

What is the relationship between wavelength and frequency in an emission spectrum?

Wavelength and frequency are inversely proportional. Signup and view all the answers

In the context of electron arrangement, what does 'EA' stand for?

Electron Arrangement Signup and view all the answers

Which of the following best describes Schrodinger's contribution to atomic theory?

He formulated the most accurate model through wave equations. Signup and view all the answers

What effect does increasing the number of electrons have on an atom's radius?

The atomic radius increases. Signup and view all the answers

What describes the relationship between energy, frequency, and Planck's constant?

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

What is the maximum number of electrons that the third shell can contain?

18 Signup and view all the answers

What characteristic of noble gases is true regarding their valence electrons?

They have 8 valence electrons. Signup and view all the answers

How does the first ionization energy change as you move down a group in the periodic table?

Decreases Signup and view all the answers

What is the significance of electronegativity in determining bond type?

It helps predict the bond's ionic character. Signup and view all the answers

What is the electronegativity value of caesium on the Pauling scale?

0.8 Signup and view all the answers

In which scenario would ionic bonding most likely occur?

When the electronegativity difference is greater than 1.8 Signup and view all the answers

What is the oxidation number of an element that achieves noble gas configuration by losing 3 electrons?

+3 Signup and view all the answers

Which statement about core electrons is correct?

They are located in inner shells. Signup and view all the answers

What does the octet rule state about elements in the same group?

They have the same number of valence electrons. Signup and view all the answers

In the context of ionic compounds, what is the purpose of using brackets in dot-and-cross diagrams?

To denote ionic interactions between charged atoms. Signup and view all the answers

Which of the following statements is correct regarding covalent bonds?

Double bonds are represented by two electron pairs. Signup and view all the answers

What does OILRIG stand for in the context of redox reactions?

Oxidation Is Loss, Reduction Is Gain. Signup and view all the answers

Which of the following correctly describes a lone pair in Lewis structures?

It is shown as two dots side by side. Signup and view all the answers

Study Notes

Unit 8 – Why do electrons matter?

Unit 8 explores the significance of electrons in various chemical contexts.

Unit 7 Recap

Atoms consist of protons, neutrons, and electrons.
Atomic mass (AR) is calculated as the sum of protons and neutrons.
Alpha decay is a type of radioactive decay where an atomic nucleus emits an alpha particle, causing a change in the mass number and atomic number of the decaying nucleus.

Unit Outline

Factual: The main energy level influences atomic reactivity and electron arrangement representation is important.
Conceptual: Electron shell organization determines an atom's oxidation state.
Debatable: The ability to control reduction-oxidation of metals could define human progress.

Atomic Structure

Physicists made significant advancements in understanding atomic structure.
Thomson proposed the plum pudding model.
Rutherford suggested atoms have a dense nucleus.
Bohr described electrons as occupying orbits around the nucleus.
Electrons can absorb specific energy levels (quantum).
The Schrodinger wave equation is the most accurate model to date.

Atomic Structure (continued)

Electrons can be excited and release energy when decaying.
Different elements absorb different amounts of energy due to distinct energy level variations.

Energy level and atom's reactivity

Create two tables in your notebook.
The first table should contain a compound name, chemical formula and observations.
The second table should detail wavelength, colour interval/nm, and frequency interval/THz associated with different colours.

Flame Test – Discussing Observations

Investigate the reason behind colour changes observed in metal and non-metal flame tests.
Analyze whether the effect is due to a physical change or chemical reaction.
Use the table to associate particular wavelengths with colours.
Evaluate the applicability of this method/test in fireworks.

Emission Spectra

Wavelength and frequency are inversely proportional.
The speed of light (c) is 3.00 x 10⁸ m/s.
Frequency is denoted by (f) and is also related to energy (E=hxf).
Planck's constant (h) is 6.63 x 10⁻³⁴ Js.

Unit 7 Review - Practice Problems

Complete problems on page 164 numbered 1, 3, 4, 6, 7, 9, 11, and 14.

Atomic radius

Atoms increase in size with increasing electron addition.
Different periodic table elements and groups have varied atomic radii sizes.

Octet rule

Electrons prioritize orbits closest to the nucleus.
Circular disks represent energy levels.
The first energy level holds 2 electrons and the second holds 8.

Electron arrangement (EA)

Electron arrangement (EA) facilitates electron configuration representation.
Group electrons together, separating them with commas.
Use resources, including videos like https://www.youtube.com/watch?v=hSkJzE2Vz_w, to assist in understanding electron arrangements.
Elements in the same column/group share the same number of valence (outermost) electrons.

Patterns

The outermost shell is called the valence shell.
It contains valence electrons.
Noble gas elements (excluding He) generally have 8 valence electrons.
2n² describes the maximum number of electrons in any shell where n is the shell number.
Shells aren't always filled immediately to their full capacity.
Inner shell electrons are referred to as core electrons.

Atomic radius (continued)

Atomic radius decreases across periods.
This relates to increasing nuclear charge.
Increased shielding from core electrons plays a role as well.
Elements show increased radii down groups.

Ionization Energy

Ionization energy (IE) is the energy needed to remove an electron from a neutral atom.
Ionization energy decreases down the groups and increases across periods.
Outermost electrons are held by the nucleus and their proximity influences the energy required for removal.

Electronegativity (x)

Electronegativity helps predict bond types (ionic or covalent).
Electronegativity is the ability of an atom to attract electrons in a chemical bond.
Differences in electronegativity values predict the nature of the chemical bond between elements. Higher difference in electronegativity value means ionic bonding.

Pauling scale

Electronegativity values are dimensionless and range from 0.8 to 4.0.
Fluorine has the highest electronegativity in the Pauling scale.
Caesium has the lowest electronegativity in the Pauling scale.
The larger the difference in electronegativity between atoms, the more ionic the bond character.
Ionic bonding occurs when the electronegativity difference between atoms is greater than 1.8.

Valence

Elements within the same group share a similar number of valence electrons.
Some elements lose electrons and others gain electrons to form ions.
The oxidation number of an atom in a chemical compound represents the number of electrons lost or gained by an atom during a chemical reaction.

Valency (continued)

Valency is related to the oxidation number (but not the same thing).
Transition metals have variable valency.
Copper forms copper(I) and copper(II) ions.
Electron arrangement notation only works well for a particular number of elements.
The third electron shell can hold up to 18 electrons.

Dot and cross diagrams

Diagrams to represent electron shell expansion.
Used to show how atoms form bonds and compounds.
Describe how atoms of differing valencies form compounds.
Use OILRIG: Oxidation Is Loss, Reduction is Gain
Show electrons lost or gained when forming compounds.

Dot-and-cross diagrams for ionic compounds

Brackets denote ionic bonds.
Electrons are not shared in ionic compounds.

Diagrams for multiple covalent bonds

Double and triple bonds are represented by four and six closely grouped electrons.

Lewis structures

Alternative method to depict the octet rule.
Focus on valence electrons.
All elements within the same group have the same number of valence electrons.
Lewis structures use dots to represent valence electrons.

Lewis structures (Continued)

Paired electrons are represented as two dots.
Non-bonding electrons are referred to as "lone pairs."
Unpaired electrons are shown as single dots.
Brackets are used for ionic bonds in Lewis structure representations.

Water - Worked Example

A detailed step by step guide/worked example to draw a Lewis structure for water (H₂O).

Redox reactions with Lewis structures

Redox reactions involve the transfer of electrons.
Oxidation involves the loss of electrons, reduction involves the gain of electrons.
OILRIG is a helpful acronym for remembering the terminology.

Homework - Practice Lewis structures

Draw Lewis structures for water (H₂O), Nitrogen trichloride (NCI₃) and Carbon dioxide (CO₂).

Practicing Lewis Structures

Instructions and information to practice drawing Lewis structures are given.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Dive into the significance of electrons in various chemical contexts in Unit 8. This quiz covers key concepts such as atomic structure, electron arrangement, and their role in atomic reactivity and oxidation states. Test your understanding of how advancements in atomic theory have shaped our current knowledge.