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There are on the whole scientific and literary material. There are for the most part books, references, questions, and many documents such as PPT., DOCX., and PDF., which additionally contain clarifications.
-It is a substance made from only one type of atom.
Example
-Carbon is made entirely from carbon atom.
-Sodium is made entirely from sodium atoms.
Unlike compound an element cannot be broken down (chemically) into more simple substance.
We know that periodic table show all elements
Atoms of the same element have the same number of protons and same atomic number.
There are 118 elements that have been identified.
the first 92 occur naturally on Earth with the remaining being synthetic elements.
There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes, which decay over time into other elements.
Compound
-Definition
molecule is the general term used to describe any atoms that are connected by chemical bond.
every combination of atoms is a molecule.
a compound is a molecule made of atoms from different elements.
All compounds are molecules, but not all molecules are a compound
Example:
-hydrogen gas is (h2) is a molecule.
-water (h2o) can be called molecule or a compound.
Electrolysis
-Electric cell
An electrical cell is a device that is used to generate electricity, or one that is used to make chemical reactions possible by applying electricity
-Galvanic cell (voltaic cell)
Is an electrochemical cell that uses spontaneous redox reactions to generate electricity.
It produces current when an oxidation–reduction reaction proceeds spontaneously.
Electrolytic cell
Electrolytic cell
-is an electrochemical cell that undergoes a redox reaction when electrical energy is applied.
-It is used to decompose chemical compounds, in a process called electrolysis.
-it uses electrical energy to produce chemical change.
-it consists of two electrodes (cathode and anode) and an electrolyte.
-reactions using electrolytic cells must be electrically induced and its anode and cathode are reversed -(anode on the left, cathode one the right).
Electrolysis
is the process by which ionic substances are decomposed?
(broken down) into simpler substances when an electric current is passed through them
-The process of electrolysis involves forcing a current produce a chemical change for which the through a cell-to-cell potential is negative; that is electrical work causes an otherwise, nonspontaneous chemical reaction to occur.
For electrolysis to work:
the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted.
Example:
if electricity is passed through molten lead bromide, the lead bromide is broken down to form lead and bromine
Chemical formula
-Importance of Chemical Formulae
Chemical formulae provide insight into the chemical composition of a compound.
They also represent the ratios in which the constituent elements combine to form the compound.
The chemical formula of a compound is crucial while representing it in a chemical equation.
Chemical formulae can also be employed to represent ions, free radicals and other chemical species.
Types of Chemical Formulae
While the term ‘chemical formula’ typically refers to the molecular formula of a compound (which denotes the total number of atoms of each constituent element in one molecule of the compound), the compositions of chemical compounds can be expressed in several ways, as listed in this subsection.
-Molecular Formula:
The molecular formula provides insight into the number of elements present in a compound. In molecular formulae, the elements are denoted by their respective symbols (as in the periodic table) and the number of atoms of each element in the molecule is written in subscript. For example- the molecular formula for glucose is C6H12O6.
-Empirical Formula:
The empirical formula of a chemical compound represents the ratio of the elements present in that compound. Empirical formulae are usually obtained based on the analysis of experimental data. The empirical formula for glucose is CH2O. Empirical Formulae can be derived from the molecular formulae.
-Structural Formula:
As the name suggests, the structural formula of a chemical compound provides insight into the arrangement of the atoms in the molecule.
Chemical equation
A chemical reaction is described by a chemical equation that gives the identities and quantities of the reactants and the products. In a chemical reaction, one or more substances are transformed to new substances. A chemical reaction is described by a chemical equation, an expression that gives the identities and quantities of the substances involved in a reaction. A chemical equation shows the starting compound(s)—the reactants—on the left and the final compound(s)—the products—on the right, separated by an arrow. In a balanced chemical equation, the numbers of atoms of each element and the total charge are the same on both sides of the equation. The number of atoms, molecules, or formula units of a reactant or product in a balanced chemical equation is the coefficient of that species. The mole ratio of two substances in a chemical reaction is the ratio of their coefficients in the balanced chemical equation.
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