Notes, summaries, assignments, exams, and problems for Chemistry

Ionic Bonds: Electron Transfer

Ionic bonds form when electrons are transferred between atoms, resulting in positively charged cations (+) and negatively charged anions (-).

Covalent Bonds: Electron Sharing

Covalent bonds form when atoms share electrons. This can be visualized by connecting the dots in Lewis structures.

Electronegativity Difference (|ΔEneg|) and Bond Type

• 2.1 - 3.3: Ionic
• 1.7 - 2.0: Borderline (use other information, e.g., boiling/melting points)
• 0.4 - 1.6: Polar Covalent
• 0.0 - 0.3: Non-Polar Covalent

Drawing Covalent Bonds (Lewis Structures)

1. Place the least electronegative element (not Hydrogen) in the center. Count the total number of valence electrons for all atoms.
2. Connect other atoms to the central atom with single bonds (one shared

Tension is a type of stress that a structural element experiences when subjected to two equal and opposite forces pulling outwards along the same axis.

These forces:

• Act on either side of the element.
• Are equal in magnitude.
• Are aligned along the element's axis.
• Pull in opposite directions.

If these forces deform the element, it will stretch. If the element fails, it will break in the middle, perpendicular to the force direction.

Compression is a type of stress that a structural element experiences when subjected to two equal and opposite forces pushing inwards along the same axis.

These forces:

• Act on either side of the element.
• Are equal in magnitude.
• Are aligned along the element's axis.
• Push in opposite directions.

If these forces deform the element,... Continue reading "Structural Element Behavior Under Different Forces" »

- Without H20 being polar, there would be no life on Earth, and Earth will be very dry. Humans and living organisims depend on H20 and it's polarity to sustain life on Earth because h20 wouldnt be able to form hydrogen bonds because it isnt polar. Animals who depend on ice such as polar bears and seals wold not be able to live due to ice not floating on the surface of water. When ice lacks crystal lattice structure, it starts to drown, and this happens due to the lack of hydrogen bonding. Therefore, h20 is very important for life to exist on earth.

- h-h: nonpolar covalent bond

- p-cl: covalent

- na-br: ionic

Electronegativity: 0->0.4 = covalent, 0.5->1.7=polar covalent, more than 1.7= ionic bonds, minus the EN

- Ion-induced dipole force:

DISTILATION PROCESS: ELEMENTS

• Thermometer: measure the temperature of the vapor
• The stopper: hold the thermometer
• The Bunsen Burner: heat the liquid
• The tube at the top of the condenser: conduct the cool water away
• The cool water: cool the vaporized alcohol
• The tube at the bottom of the condenser: conduct cool water in
• The receiving flask: collect the condensed alcohol
• The stand (soporte): maintain an upright or vertical position
• The clamps (pinzas): support the wire
• The wire gauze (rejilla de alambre): spread the flame out
• The ring clamps (pinzas de anilla): grip the flask and the condenser

ORDER

1. Distillation is used...
2. To separate a mixture of liquids...
3. Distillation is a widely used method...
4. The gas is then condensed...
5. Although the term is mostly common.

Electrolysis of Molten Sodium Chloride

Example: Molten sodium chloride:

• Cathode: 2H⁺(aq) + 2e^- → H₂(g) (hydrogen bubbles off)
• Anode: 2Cl^- → Cl₂(g) + 2e^- (chlorine gas produced)

Electrolysis of Aqueous Sodium Chloride

Aqueous solution of sodium chloride:

• At the cathode: Na⁺ and H⁺(aq) are present. H⁺(aq) is discharged because hydrogen is below sodium in the reactivity series. 2H⁺(aq) + 2e^- → H₂(g)
• At the anode: OH^- and Cl^- are present. Cl^- is discharged because it is in high concentration. 2Cl^-(aq) → Cl₂(g) + 2e^-

Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.

Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidized.

Brine

What is an atom?

Atoms are the basic units of matter and the defining structure of elements.

What is an electron?

A subatomic particle with a charge of negative electricity.

What is the nucleus of an atom made of?

Is made up of protons and neutrons.

What is a proton?

Elemental particle of the nucleus of the atom and that has a positive electric charge.

What is a neutron?

A subatomic particle of about the same mass as a proton but without an electric charge.

Where is the mass of an atom concentrated?

In the nucleus most of 99.9% of the mass is concentrated here.

An atom is mostly empty space?

Yes.

What is the function of neutrons?

To allow protons to be together.

What surrounds the nucleus of an atom?

The nucleus is surrounded by electron clouds that produce... Continue reading "Understanding Atoms and Quantum Mechanics: A Comprehensive Guide" »

In the periodic table, elements are classified into metals, nonmetals, and metalloids. Metals are ductile, malleable, shiny, are good conductors for heat and electricity. All metals are solids at room temperature and pressure except, Mercury. Nonmetals exist as solids, liquids, or gases. A liquid non-metal at room temperature and pressure is Bromine.

2. The elements in the d-block in the periodic table have several characteristics in common.

(i) Give the electron configuration of N²⁺

1S2 2S2 2P3- 2= 1S2 2S2 2P1

(ii) Explain what is meant by a ligand and describe the type of bond formed between a ligand and a d-block element.

It is an atom or molecule with a lone pair of electrons that combine with a metal through coordinate covalent bonding. In transition... Continue reading "Chemistry Basics: Metals, Nonmetals, and Transition Elements" »

Electricity and Atoms

Electricity is an electric charge. But there is much more behind than the simple statement:

• Where do the charges come from?
• How do we move them? Where do they move?
• How does an electric charge cause mechanical movement or invent things?

Atoms and Charge

To understand it we start with atoms, one of the basic blocks of life and matter. An atom is three different particles: electrons, protons and neutrons. Each atom has a central nucleus, where protons and neutrons are attached. Around the nucleus there is a group of electrons in orbit. The number defines which chemical element the atom represents. This set is called the atom's atomic number. Electrons are the operation of electricity In its most stable and balanced state, an atom... Continue reading "Understanding Electricity: Atoms, Charge, and Flow" »

• Metal + nonmetal = ionic bond

•  Nonmetal + nonmetal = covalent bond  

•  Metal + metal = metallic bond

• Electron filling pattern: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f

• Physical Changes

  • Do not create a new substance.

• Chemical Changes - Do produce new substances.

•  Ions - Atoms can gain or lose electrons to form ions (atoms with a charge. 

• • Anion - Atom with a negative charge. 

• • Cation - Atom with a positive charge.
  

• quantitative= number/amount, qualitative= observation of physical change
  

• alkali metals the column of elements from lithium to francium.
  

• Alkaline earths the column of elements from beryllium to radium.
  

• Halogens the column of elements from fluorine to astatine.
  

• The Periodic Law states that the physical and