Atoms Flashcards
If the number of protons is x than the number of electrons, a positively charged ion, or x, is formed.
- greater
- cation
If the number of protons is x than the number of electrons, a negatively charged ion, or x, is formed.
- less
- anion
element definition
- simplest form of matter that retains its own unique properties, which are different from all other elements.
- The Periodic Table of the Elements lists all of the known elements in the universe.
mass vs atomic number
- Ar is number of P
- MN is number of P+N
mixture defintion
- Mixtures involve two or more substances that are physically mixed or intermingled.
- However, these substances are not chemically bonded together. Therefore, the substances can be present in any ratio.
homogenous mixture def
- has the same composition throughout the entire mixture.
- if you take a sample from any part of the mixture, it will look and be the same.
Examples:
- Salt water: Once the salt dissolves in the water, the mixture looks uniform, and you can’t see or separate the salt from the water by looking at it.
heterogeneous mixture def
- has a non-uniform composition, meaning that different parts of the mixture may look or behave differently.
- Examples:
Salad: Each part of a salad might have different ingredients, like lettuce, tomatoes, cucumbers, etc. The composition changes from one bite to another.
Which of the following descriptions is used to describe the liquid state?
- Matter in this state has a definite volume, and the shape is determined by the container.
- In a liquid, the particles are attracted to one another causing them to “stick” together.
- causes liquids to have a defined volume. However, the particles are able to slowly move in random directions throughout the space they occupy.
*****Solids have a definite shape and definite volume, whereas the volume and the shape of a gas are both determined by the container.
An ion has a 2+ charge and 18 electrons. What is the identity of the element?
The element is Ca.
- If an ion has a 2+ charge, then the atom lost 2 e- to form the ion.
- If the ion has 18 electrons after losing two, then it must have started with 20 electrons
Consider the following designation for an isotope of potassium-40:
What numbers should be used for the letter “A” and the letter “Z”?
What symbol should be used for the letter “X”?
- Potassium-40 has a mass number of 40, which corresponds to the letter “A” and an atomic number of 19,
- which corresponds to the letter “Z.” The chemical symbol for potassium is “K”, which corresponds to the letter “X.”
A – 40
Z – 19
X – K
Consider the following designation for an isotope of phosphorus-31:
What numbers should be used for the letter “A” and the letter “Z”?
- Phosphorus-31 has a mass number of 31 and an atomic number of 15.
- The mass number is always written above the atomic number and before the elemental symbol.
Isotope
They are the same element with the same number of protons but a different number of neutrons, resulting in a different mass number.
gas state defintion
Matter in this state has a definite volume, and the shape is determined by the container.
how to find molecular gemotry
***Use the Steric Number (SN): SN = Numberofbonds + Numberoflonepairs
- Count bonds (single, double, triple) and lone pairs as separate regions of electron density.
SN = 2 → Linear → 18 0 ∘
SN = 3 → Trigonal planar → 120 ∘
SN = 4 → Tetrahedral → 109. 5
SN=5 → Trigonal bipyramidal.
SN = 6 SN=6 → Octahedral.
Rules to Identify the Central Atom
- H+ is Never the Central Atom: cause only forms one bond, so it’s always on the outside.
- Atoms with lower electronegativity (like C) are more likely to be central because they can share their electrons more easily.
- Oxygen, Nitrogen, or Halogens (e.g., Cl, F) Are Usually Outer Atoms:
- If there’s one atom of a certain element (e.g., carbon in
CH4, it’s usually the central atom.
Single bond vs double bond
- A SB involves 2 e- shared between two atoms e.g H-H beacuse Each hydrogen contributes 1 electron.
- A DB involves 4 e- shared between two atoms. e.g
C=O in carbon dioxide beacuse Carbon and oxygen each contribute 2 electrons.
octet rule
-means an atom wants 8 total electrons around it
- Shared e- in bonds.
- Lone pairs (non-bonding electrons the atom “keeps” to itself).
lone pairs using example of oxygen
- e- in the Outer Shell: O2 has 6 valence electrons (outer shell electrons) because it’s in Group 16 of the periodic table.
- Oxygen typically forms 2 bonds to get 8 electrons and satisfy the octet rule
- When O2 bonds with another atom, it uses some of these 6 electrons to form bonds.
- The remaining electrons that don’t form bonds stay as lone pairs.
dipole moment
- an uneven distribution of electrons in the molecule.
- happens when the bonds are polar (e.g., a bond between atoms with different electronegativities).
- If the molecule’s overall geometry cancels out these polarities (symmetry), the dipole moment becomes 0.
Electronegativity increases as you move… and examples
- Across a period (left to right).
- Up a group (bottom to top).
- Fluorine (F) is the most electronegative element.
- Oxygen ( O) , nitrogen ( N ) and chlorine ( Cl) are also highly electronegative.
- Carbon ( C ) and hydrogen ( H) have lower electronegativities.
Pualing scale of electroneg + example of how to calc
Hydrogen ( H) = 2.1
Carbon ( C) = 2.5
Chlorine ( Cl) = 3.0
Oxygen ( O) = 3.5
Fluorine ( F) = 4.0 (the highest).
Subtract the smaller electronegativity value from the larger one.
For C-Cl:
Electronegativitydifference = 3.0 ( Cl ) − 2.5 ( C ) = 0.5 Electronegativitydifference=3.0(Cl)−2.5(C)=0.5 Since 0.5 > 0.4 0.5>0.4, C-Cl C-Cl is a polar bond.
