L1 - Atoms, Bonding, and the Periodic Table
Define valence electron
Valence electrons are the electrons in an atom's outermost energy level, or orbit.
When an atom loses or gains electrons, it becomes _____
When an atom loses or gains electrons, it becomes an ion
A covalent bond in which electrons are shared equally is called a ______
nonpolar bond
The metal atoms in iron are held together by ____
metallic bonds
What is an element's atomic number determined by?
The atomic number of an element is determined by its number of protons.
What is the structure of an atom? What charges does each part of the atom have?
At the center of the atom is a tiny, dense nucleus containing protons and neutrons. Surrounding the nucleus is a cloudlike region of moving electrons.
Protons are positive, neutrons are neutral, and electrons are negative.
What form do ionic compounds take?
Ionic compounds form crystals, orderly , three-dimensional arrangements of positive and negative ions.
What is a triple bond? How is it similar and different to a single bond?
A triple bond is when 3 pairs of electrons (6 total shared electrons) are shared between two atoms. Single bonds share only 1 pair of electrons (2 total shared electrons).
Polished metals have a metallic luster, which means that _______
Polished metals have a metallic luster, which means that they are shiny and reflective
Molecules are joined together using _____
covalent bonds
When atoms react, they form a chemical bond, which is defined as _____
When atoms react, they form a chemical bond, which is defined as the force of attraction that holds atoms together
How does losing and electron affect the charge of the atom? What does it become?
How does gaining and electron affect the charge of the atom? What does it become?
When an atom loses an electron, it becomes a positive ion. When an atom gains and electron, it becomes a negative ion.
An oxygen atom can form two covalent bonds. How many valence electrons does an oxygen atom have?
Oxygen has 6 valence electrons, meaning it can form two covalent bonds because it can hold two more electrons.
Name three of the properties of metal.
1. Luster - shiny and reflective
2. Malleable - can be beaten into different and complex shapes
3. Ductility - can be bent easily and pulled into thin strands or wires
4. Thermal Conductivity - heats and cools very quickly.
5. Electrical Conductivity - can conduct and carry electric currents easily.
Sodium Chloride is an example of an ionic compound, which is composed of ______
Sodium Chloride is an example of an ionic compound, which is composed of positive and negative ions
Atoms try to become stable by ______
Atoms try to become stable by reaching 8 valence electrons. Some elements, like chlorine, try to take valence electrons because they are already close to 8. Other elements, like sodium, have very few try to lose valence electrons to get to 8, because when they can go down to their next electron shell.
Explain why ionic compounds have high melting points.
The attraction between the positive and negative atoms in ionic compounds is extremely strong, meaning it takes a huge amount of energy to separate the ions in a crystal. As a result, ionic compounds have very high melting points
Explain the difference between nonpolar and polar molecules. What is one example of a nonpolar molecule?
Nonpolar bonds are covalent bonds that share electrons equally. They have a neutral charge.
Polar bonds are covalent bonds where electrons are shared unequally. The atom that pulls the electrons more becomes slightly negative, and the atom that pulls the electron less becomes slightly positive. Water (H2O) is a polar molecule.
Why does an aluminum horseshoe bend but not break when a blacksmith pounds it into shape with a hammer?
Metallic bonds are very malleable, meaning they can be beaten into different shapes. this is because when the metal is pounded, the positive ions can change position, but the bonds between the ions and the freely moving valence electrons keep the metal ions from breaking apart.
What is the electron sea?
The electron sea is the valence electrons that drift among the positive ions of a metal crystal.
Elements in which group on the periodic table are least likely to react with other elements? Why is this the case?
Elements in group 18 of the periodic table are very unlikely to react with other elements because they already have 8 valence electrons. We can see this very easily because it is in group 18 of the periodic table. Atoms are most stable when they have 8 valence electrons and don't want to react.
Describe how an ionic bond forms as the atoms react. Say what happens to the valence electrons in each atom and how each atom is changed by losing or gaining electrons.
Ionic bonds form when atoms that easily lose electrons react with atoms that easily gain electrons. Valence electrons are transferred from one atom to the other. The atom that lost electrons becomes a positive ion, and the atom that gained electrons becomes a negative ion. The two oppositely charged ions are attracted like a magnet, forming an ionic bond
Explain what a covalent bond is and how they hold atoms together.
Covalent bonds are the chemical bond formed when two atoms share electrons. The attractions between the shared electrons and the protons in the nucleus of each atom hold the atoms together.
Explain how metallic bonds hold atoms together.
Metallic bonds are held together by the attraction between the positive ions and the negative electrons that drift between them.