A spouse can receive up to half of the retirement/disability benefit being paid to the primary recipient. There are certain guidelines, however, to be eligible to collect benefits.
To receive benefits as the spouse of a recipient, one must be at least 62 years old.
You can also receive benefits as the ex-spouse of a recipient. In that scenario you must have been married at least 10 years, been divorced for at least two years, be at least 62 years old, and not be eligible for an equal or higher benefit based on your own work or someone else's work (e.g. current spouse if applicable).
Finally, you may be eligibe to collect the benefits of a deceased primary recipient as an ex-spouse. The requirements are that you be at least 60 years old (or 50 if disabled), have been married for at least 10 years, not be eligible for an equal or higher benefit based upon your own work, and not be currently married unless the remarriage occurred after age 60 (or 50 if disabled).