wk 2 Flashcards
(27 cards)
Describe the difference between a period and a group on the periodic table. What does a period correspond to?
A period is a horizontal row and corresponds to the number of electron shells. A group is a vertical column with elements that share similar properties.
Describe the steps for drawing a Bohr Model.
1) Draw the nucleus with protons and neutrons. 2) Add electron shells around the nucleus. 3) Fill in electrons based on the energy levels: 2 in the first shell, 8 in the second, 18 in the third.
What are valence electrons? Why are they important?
Valence electrons are electrons in the outermost shell. They are important because they determine how atoms bond and react with other atoms.
Explain the difference between a molecule and a compound. Give an example of each.
A molecule is two or more atoms bonded together (e.g., O₂). A compound is two or more different elements bonded together (e.g., H₂O).
What is a chemical bond? Name the two types.
A chemical bond is a force that holds atoms together. The two types are ionic and covalent bonds.
What is an ionic bond? Describe how one is formed.
An ionic bond is formed when one atom donates electrons and another accepts them, creating positive and negative ions that attract.
How do we know which atom will lose or gain electrons in an ionic bond?
Metals (low electronegativity) lose electrons, and nonmetals (high electronegativity) gain electrons.
What is a covalent bond? Describe the three types.
A covalent bond is when atoms share electrons. Types: single bond (one pair shared), double bond (two pairs shared), triple bond (three pairs shared).
What is a hydrogen bond? How is this bond different from the previous two?
A hydrogen bond is a weak attraction between a hydrogen atom and another electronegative atom. It’s weaker than ionic or covalent bonds.
When is an atom stable or unreactive?
When its outermost electron shell is full (achieving an octet).
What is the octet rule? How do atoms achieve an octet?
Atoms aim to have 8 electrons in their outer shell by gaining, losing, or sharing electrons.
Which atoms are the exception to the octet rule? Why?
Hydrogen and helium; they are stable with 2 electrons.
Which group on the periodic table are the noble gases? Why are they called that?
Group 18; they are called noble because they are inert and rarely react.
What is electronegativity? Why is it important?
Electronegativity is an atom’s ability to attract electrons. It helps predict bond type and molecule behavior.
Place in increasing order of electronegativity: F, N, Si, C, O.
Si < C < N < O < F.
What type of bond occurs when: Large electronegativity difference? Small to no difference?
Large electronegativity difference: Ionic bond. Small to no difference: Covalent bond.
Describe a nonpolar covalent bond. Sketch electron cloud.
Electrons are shared equally. (Sketch: symmetrical cloud around both atoms.)
Describe a nonpolar molecule. Sketch example.
A molecule with no charge separation (Example: O₂).
Describe a polar covalent bond. Sketch electron cloud.
Electrons are shared unequally, creating slight charges. (Sketch: more dense electron cloud near one atom.)
Describe a polar molecule. Sketch example with charges.
A molecule with partial positive and negative ends (Example: H₂O, δ+ H and δ- O).
What properties of water are the result of its polarity?
Cohesion, adhesion, high surface tension, and solvent ability.
Describe an ionic bond. Sketch electron cloud.
One atom transfers electrons completely to another (Sketch: electron cloud moved from one atom to another, creating ions).
How can we predict the number of bonds an atom will form?
By the number of electrons needed to complete its octet.
Describe the difference between a molecular and a structural formula. Give examples.
Molecular: shows number and type of atoms (e.g., H₂O). Structural: shows arrangement of atoms (e.g., H–O–H).
