There are several ways depending on what you are using. If you are wanting to query the daemon - one must assume you are running a Linux box or VPS

You do not want or need an " address balance " - you need YOUR wallet balance

This question has already been partially answered here => How would one monitor an address for a transaction and 1 confirmation in PHP?

The best way however is to use what the Electrum docs recommend - a curl call like this => curl --data-binary '{"id":"curltext","method":"getbalance","params":{"funded":true}}' http://127.0.0.1:7777

If you are using PHP - it would look something like this:

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, "http://127.0.0.1:7777");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, "{\"id\":\"curltext\",\"method\":\"getbalance\",\"params\":{\"funded\":true}}");
curl_setopt($ch, CURLOPT_POST, 1);

$headers = array();
$headers[] = "Content-Type: application/x-www-form-urlencoded";
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

$result = curl_exec($ch);
if (curl_errno($ch)) {
    echo 'Error:' . curl_error($ch);
}
curl_close ($ch);

You could make this inside a try-catch and trigger it by a cron job running at whatever interval you want to check

What comes back is a JSON-RPC file which you can decode into an array

$result =  json_decode($response, true);

and plug that into another variable for the single thing or things you want to work on from there

$wanted = $result["result"]["xxxxxxxxx"];

any of the parameters can be passed as a variable to the curl call

for instance to add a request it would go like this:

curl_setopt($ch, CURLOPT_POSTFIELDS, "{\"id\":\"curltext\",\"method\":\"addrequest\",\"params\":{\"amount\":\"$how_much\",\"memo\":\"$your_memo->some_data_field\"}}");

You just need to run a "getbalance " - or any - command see what it returns and adjust your code to pull the returned value from "result" - you just test for a greater than " 0 " and then empty the wallet by sending it to another wallet and wait for the next payment

You could then use that data to trigger a "do something" like the email example in the above link from the middle example there.

Jirico's answer is the right one. Gotta make sure you put the address you're querying in params.

If you need more depth than just a balance, you can also getaddresshistory

{"id":"myquery","method":"getaddresshistory","params":["14vuRY354EaxDu4WrgjtvoDEwntDNwMVbx"]}

You can find a list of commands here: An Introduction to the Electrum Python Console