2−(−4)+3+(−6)−(−2)2, minus, left parenthesis, minus, 4, right parenthesis, plus, 3, plus, left parenthesis, minus, 6, right parenthesis, minus, left parenthesis, minus, 2, right parenthesis.

7

Step-by-step explanation:

2−(−4)+3+(−6)−(−2)2

solution:

– x – = +

– x + = –

= 2−(−4)+3+(−6)−(−2)2

= 6 + 3 + ( – 6) – ( 2 ) 2

= 9 + ( –6 ) – ( –2 ) 2

= 3 – (–2)2

= 3 – ( –4 )

= 7

ISOTOPES:

Elements having same atomic number but different atomic masses are known as Isotopes.

Example:

Carbon-12, Carbon-13, Carbon-14 are thee isotopes of carbon atom. Here 12, 13 and 14 are the atomic masses of isotopes of carbon respectively. Since, atomic number is the unique property of an atom, thus the atomic number of carbon is 6 even in the case of three types of carbon (isotopes)

126Carbon, 136Carbon, 146Carbon are 3 isotopes of Carbon.

Hydrogen-1, Deuterium–2, Tritium-3 are three isotopes of hydrogen.

ISOBARS:

Elements having same atomic mass and different atomic numbers are known as Isobars.

Example:

4018Ar (Argon) and 4020Ca (Calcium)

Both the elements have same atomic mass equal to 40 but different atomic numbers, i.e. argon has atomic number equal to 18 and calcium has atomic number equal to 20.