A: An element is a substance that can’t be broken down to other substances by chemical reactions. A compound is a substance consisting of two or more different elements combined in a fixed ratio.
Q: What are the subatomic particles?
A: Subatomic particles are the particles composing nucleons and atoms.
Q: What is a covalent bond?
A: A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds.
1. An atom is the smallest unit of matter that still retains the properties.
2. An element’s properties depend on the structure of its atoms.
3. A bond in which electrons are shared equally is a nonpolar covalent bond; a bond which electrons are not shared equally called a polar covalent bond.
4. A molecule’s shape determines the positions of its atom’s valence orbitals.
5. Chemical reactions change reactants into products while conserving matter.
Figure 2.5
Simplified models.
The ones in the middle are the nucleus and this model of a helium atom has two electrons
The nucleus here has 2 neutrons and 2 protons. The two electrons are outside the nucleus.
This chapter is about elements and their structures. Elements are very interesting because of all their particles and many different groups. In an atom, electrons occupy specific energy shells; the electrons in a shell have a characteristic energy level.
Then, there are covalent bonds, ionic bonds, and weak chemical bonds. Covalent bonds are chemical bonds that form when atoms interact and complete their valence shells. Covalent bonds form when pairs of electrons are shared. Ionic bonds are when an atom transfers its electrons and both the atoms become ions, complete ones. A weak chemical bond is considering the hydrogen bonds.
Key terms
Compound: is a substance consisting of two or more different elements combined in a fixed ratio
Neutron: a subatomic particle having no electrical charge, found in the nucleus of an atom.
Protons: a subatomic particle with a single positive electrical charge.
Electrons: a subatomic particle with a single negative electrical charge, one or more electrons move around the nucleus of an atom.
Dalton: a measure of mass for atoms and subatomic particles.
Atomic number: all atoms of a particular element have the same number of protons in their nuclei, the number of protons, which is unique to that element, is called the atomic number.
Mass number: is the sum of protons plus neutrons in the nucleus of an atom.
Radioactive isotopes: is one in which the nucleus decays spontaneously, giving off particles and energy.
Covalent bond: a covalent bond is sharing of a pair of valence electrons by two atoms.
Ionic bond: a chemical bond resulting from the attraction between oppositely charged ions.
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