By definition, an atom is electrically neutral(i.e. has the same number of protons as it doeselectrons, plus some number of neutrons dependingon the isotope). If a species were charged, it isreferred to as an ion (cation for positivelycharged and anion for negatively charged species),also by definition.
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But this is probably not a very satisfyinganswer. (I personally find answers based ondefinitions pretty bland.) Perhaps an interestingfollow up question is...
Is the universe electrically neutral?
For many instances in science, we deal withsystems where charge neutrality is veryimportant.
Perhaps a common example you might be familiarwith is table salt, NaCl. Before formingsalt, both sodium (Na) and chlorine (Cl) areelectrically neutral atoms. Then chlorine nabs anelectron from a sodium because it is moreenergetically favorable for it to have anadditional electron. You then have a Na+ cationand Cl- anion that combine into NaCl due toelectrostatic attraction. Overall, NaCl is aneutral system (table salt doesn"t shock you whenyou eat it... hopefully).
This property of electrical neutrality is alsovery important in the work that I do every day. Ido computational research on crystals like NaClwhere we calculate energies of a variety of sortsto understand the material. Part of calculatingthe total energy of a system for a crystal likeNaCl involves the energy contribution that arisesfrom Coulombic forces between every combination ofNa+ and Cl- anion. This would mean figuring thisout for something like 1023 ions (whichis a lot). We do something a little more clever.NaCl is a crystal, which means it has a periodic(i.e. repeating) structure, so we only need toconsider a unit cell, or small portion that canreproduce the entire crystal structure bytranslating it. But this means what we model isinfinitely large materials. This is okay for bulkmaterials, since surface effects are small.
What is more worrying are those long rangeCoulombic forces. If we"re not careful, we couldend up with infinite energy! And that would be nogood. This can be solved with a clever way ofadding Coulombic forces (called Ewaldsummation) and a charge neutral unit cell.
But if many everyday things we are familiarwith are electrically neutral, does this mean thatthe universe has to be electrically neutral?Maybe.
It"s actually still an open research question.What do you think would happen if the universewere just slightly positively charged overall?This is different from being ionized- that justmeans there are positively and negatively chargedparticles. But do these particles have to justbalance each out? You can follow an interestingdiscussion hereor a pretty recent articleabout how the universe could be slightlypositively charged (the math gets a little hairytowards the end, but there luckily is moreexposition overall).
Hope this helps!Best,
Atoms are made of 3 sub-atomic (smaller than anatom) particles: neutron (neutral), protons(positive), and electrons (negative). When an atomhas the same number of protons as electrons, thecharges balance each other and the atom isneutral. If the atoms aren"t neutral, they arevery reactive and will react with nearby atoms toform compounds or perform other reactions. Becausethe air around us contains many gas molecules, anycharged atoms (called ions) will quickly react. Ifyou want to keep free ions you need to have areally good vacuum with no other atoms around thatcan react with the free ions. The opposite of freeions are bound ions, which are quite common. Theseare ions that have reacted with other atoms tomake a stable compound, like table salt, which ismade of positive sodium ions and negative chlorideions.
When an atom is electrically neutral, it meansthat the overall charge of the atom is zero. Atomsare made up of positively charged particles calledprotons and negatively charged particles calledelectrons as well as non-charged particles calledneutrons. The charge from a proton or electron areof equal strength, therefore if an atom has anequal number of protons and electrons, it will beelectrically neutral.
However, atoms are not always electricallyneutral, in which case they are called ions. Anion is an atom that has lost or gained electronsresulting in a positive charge (from losingelectrons) or a negative charge (from gainingelectrons).
They don"t have to be. In an atom, there are acertain number of positively-charged protons.Positively-charged protons attractnegatively-charged electrons, but thenegatively-charged electrons repel one-another. Asa result, the atom can attract a number ofelectrons until it has equal numbers of protonsand electrons, making the atom neutral.
There are a lot of ways to make a non-neutralatom, though. For example, table salt, in water,breaks up into negatively-charged chloride ions(chlorines with one extra electron), andpositively-charged sodium ions (sodium with onetoo few electrons). Why this happens has to dowith quantum mechanics, which is a college-levelchemistry topic. Also, high-energy light or otherforms of energy can strip the electrons fromatoms; this is why ultraviolet light causessunburn, for instance, because it strips theelectrons from the atoms in your skin.
Well, let"s think about what makes up an atom:an atoms consists of a bunch of negatively-chargedelectrons orbiting around a nucleus, which is madeup of neutral neutrons and positively-chargedprotons. In pretty much all atoms, the number ofelectrons and protons is the same, so the netcharge of the atom in zero.
But what if the atom has more or less electronsthan protons? Well, then the atom becomeselectrically charged - this is called an ion(which are super important, by the way! Ions aresuper important to a ton of stuff, includingmaking sure your body works correctly!). If theatom has more electrons than protons, it isnegatively charged, while if it has fewerelectrons than protons, it becomes positivelycharged. However, remember that opposite chargesattract and like charges repel: so, apositively charged atom will attract electronsuntil it becomes neutral, whereas a negativelycharged atom will repel some of its electronsuntil it also becomes neutral. So only neutralatoms are stable.
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Atoms are neutral if they have the same numberof charged protons and electrons, balancingpositive and negative charges. As long as thenumbers of electron and protons are the same, thecharges will balance. Sometimes atoms are morestable though when they are not perfectlyelectrically neutral. These charged atoms arecalled "ions." If you put salt in water, itsmolecules actually break apart into individuallycharged atoms. This is because water itself hasslight charges.
Atoms are electrically neutral because theyhave equal numbers of protons (positively charged)and electrons (negatively charged). If an atomgains or loses one or more electrons, it becomesan ion. If it gains one or more electrons, it nowcarries a net negative charge, and is thus"anionic." If, on the other hand, it loses one ormore electrons, it now carries a net positivecharge and is "cationic."