Mass number and atomic number are two important pieces of information about a nucleus.

You are watching: An atom has 17 protons and 18 neutrons

A nucleus can be represented using the symbol notation:

<_Z^A extrmX>

Where:

A is the mass numberZ is the atomic numberX is the chemical symbol of the elementA - Z = number of neutrons N

For example, chlorine (Cl) can be shown as: Carbon has three isotopes: (_6^12 extrmC), (_6^13 extrmC) and (_6^14 extrmC). They all barisalcity.orgntain six protons, but six, seven and eight neutrons respectively.

(_7^14 extrmN) and (_6^14 extrmC) are not isotopes.

They have the same mass number, A, but different atomic number, Z, and different chemical symbol - they are not the same element.

If the number of protons changes, then it is a different element.

Question

How many protons does (_6^14 extrmC) barisalcity.orgntain?

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The atomic number is 6 so (_6^14 extrmC) barisalcity.orgntains six protons.

Question

How many neutrons does (_6^14 extrmC) barisalcity.orgntain?

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Number of neutrons = mass number - atomic number = 14 - 6 = 8 neutrons.

Question

Write down the number of particles in the following nuclei:

<_30^64 extrmZn>

<_92^238 extrmU>

<_1^3 extrmH>

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<_30^64 extrmZn>

Number of protons Z = 30Number of protons + neutrons A = 64Number of neutrons N = 64 - 30 = 34Since this is a nucleus there are no electrons

There are 30 protons and 34 neutrons.

<_92^238 extrmU>

Number of protons Z = 92Number of protons + neutrons A = 238Number of neutrons N = 238 - 92 = 146Since this is a nucleus there are no electrons

There are 92 protons and 146 neutrons.

See more: How Much Oil Does A Lmm Duramax Hold, Duramax Fluid Capacities

<_1^3 extrmH>

Number of protons Z = 1Number of protons + neutrons A = 3Number of neutrons N = 3 - 1 = 2Since this is a nucleus there are no electrons

There is 1 proton and 2 neutrons.

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The structure of the nucleus - CCEA