Question

Which of the following statements is not correct for a compound

1. Compound is composed of two or more elements in a definite ratio.
2. Compound is composed of molecules
3. Compound can not be devided into its elements physically
4. In a compound, elements can combine in any ratio.​

Answer 1

Answer:

Explanation:Elements are the simplest complete chemical substances. Each element corresponds to a single entry on the periodic table. An element is a material that consists of a single type of atom. Each atom type contains the same number of protons.

Chemical bonds link elements together to form more complex molecules called compounds. A compound consists of two or more types of elements held together by covalent or ionic bonds.

Elements cannot be divided into smaller units without large amounts of energy. Compounds, on the other hand, can have their bonds broken with practical amounts of energy, such as the heat from a fire.

Matter can be broken down into two categories: pure substances and mixtures. Pure substances are further broken down into elements and compounds. Mixtures are physically combined structures that can be separated back into their original components.

Terms

elementAny one of the simplest chemical substances that cannot be changed in a chemical reaction or by any chemical means. Made up of atoms that all have the same number of protons.

compoundA substance made from two or more elements. Consists of a fixed ratio of chemically bonded atoms. Has unique properties that are different from the properties of its individual elements.

chemical bondAny of several attractive forces that serve to bind atoms together to form molecules.

Elements

A chemical element is a pure substance that consists of one type of atom. Each atom has an atomic number, which represents the number of protons that are in the nucleus of a single atom of that element. The periodic table of elements is ordered by ascending atomic number.

The chemical elements are divided into the metals, the metalloids, and the non-metals. Metals, typically found on the left side of the periodic table, are:

often conductive to electricity

malleable

shiny

sometimes magnetic.

Aluminum, iron, copper, gold, mercury and lead are metals.

In contrast, non-metals, found on the right side of the periodic table (to the right of the staircase), are:

typically not conductive

not malleable

dull (not shiny)

not magnetic.

Examples of elemental non-metals include carbon and oxygen.

Metalloids have some characteristics of metals and some characteristics of non-metals. Silicon and arsenic are metalloids.

As of November, 2011, 118 elements have been identified (the most recently identified was ununseptium, in 2010). Of these 118 known elements, only the first 98 are known to occur naturally on Earth. The elements that do not occur naturally on Earth are the synthetic products of man-made nuclear reactions. 80 of the 98 naturally-occurring elements are stable; the rest are radioactive, which means they decay into lighter elements over timescales ranging from fractions of a second to billions of years.